OTLP support for exporting exponential histograms

[alanwest]

This PR makes the Base2ExponentialHistogramConfiguration public. Support is added to the OTLP exporter for exporting exponential histograms.

Follow ups for other exporters

Minimal work is done in this PR to the console and Prometheus exporters so that they don't blow up. Follow ups to consider:

Prometheus exporter

Currently, the exporter ignores exponential histograms. The collector exporter logs an error. We could do the same, though it may occur frequently?

Example:

2023-03-27T18:23:00.908Z error prometheusexporter@v0.74.0/accumulator.go:105 failed to translate metric {"kind": "exporter", "data_type": "metrics", "name": "prometheus", "data_type": "\u0004", "metric_name": "http.server.duration"}

Console exporter

With this PR only the sum, count, min, and max are displayed. Buckets are not yet displayed. Two options:

1. Java's console exporter supports OTLP/JSON format, so the bucket counts just show up as an array of numbers. The JSON looks roughly like:

   "http.server.duration":{"dataPoints":[{"timeUnixNano":"10","count":"6","sum":10.0,"min":1.0,"max":5.0,"positive":{"offset":10,"bucketCounts":["1","2","3"]},"negative":{},"exemplars":[],"attributes":[],"aggregationTemporality":1}

2. The collector's logging exporter calculates the bucket boundaries for display. This can become very lengthy

Collector logging exporter example

Metric #0
Descriptor:
     -> Name: http.server.duration
     -> Description: Measures the duration of inbound HTTP 
     -> Unit: ms
     -> DataType: ExponentialHistogram
     -> AggregationTemporality: Cumulative
ExponentialHistogramDataPoints #0
Data point attributes:
     -> http.flavor: Str(1.1)
     -> http.method: Str(GET)
     -> http.route: Str(WeatherForecast)
     -> http.scheme: Str(https)
     -> http.status_code: Int(200)
     -> net.host.name: Str(localhost)
     -> net.host.port: Int(5001)
StartTimestamp: 2023-03-27 18:20:00.912126 +0000 UTC
Timestamp: 2023-03-27 18:23:00.890708 +0000 UTC
Count: 9
Sum: 2854.493000
Min: 161.128000
Max: 523.119000
Bucket [160.688737, 162.438523), Count: 1
Bucket [162.438523, 164.207362), Count: 0
Bucket [164.207362, 165.995463), Count: 0
Bucket [165.995463, 167.803035), Count: 0
Bucket [167.803035, 169.630290), Count: 0
Bucket [169.630290, 171.477443), Count: 0
Bucket [171.477443, 173.344710), Count: 0
Bucket [173.344710, 175.232310), Count: 0
Bucket [175.232310, 177.140465), Count: 0
Bucket [177.140465, 179.069398), Count: 0
Bucket [179.069398, 181.019336), Count: 0
Bucket [181.019336, 182.990507), Count: 0
Bucket [182.990507, 184.983143), Count: 0
Bucket [184.983143, 186.997478), Count: 0
Bucket [186.997478, 189.033747), Count: 0
Bucket [189.033747, 191.092189), Count: 0
Bucket [191.092189, 193.173047), Count: 0
Bucket [193.173047, 195.276563), Count: 0
Bucket [195.276563, 197.402986), Count: 0
Bucket [197.402986, 199.552563), Count: 0
Bucket [199.552563, 201.725548), Count: 0
Bucket [201.725548, 203.922195), Count: 0
Bucket [203.922195, 206.142762), Count: 0
Bucket [206.142762, 208.387510), Count: 0
Bucket [208.387510, 210.656701), Count: 0
Bucket [210.656701, 212.950602), Count: 0
Bucket [212.950602, 215.269482), Count: 0
Bucket [215.269482, 217.613613), Count: 0
Bucket [217.613613, 219.983270), Count: 0
Bucket [219.983270, 222.378731), Count: 0
Bucket [222.378731, 224.800277), Count: 0
Bucket [224.800277, 227.248191), Count: 0
Bucket [227.248191, 229.722762), Count: 1
Bucket [229.722762, 232.224278), Count: 0
Bucket [232.224278, 234.753035), Count: 0
Bucket [234.753035, 237.309328), Count: 1
Bucket [237.309328, 239.893457), Count: 0
Bucket [239.893457, 242.505726), Count: 0
Bucket [242.505726, 245.146440), Count: 0
Bucket [245.146440, 247.815910), Count: 0
Bucket [247.815910, 250.514448), Count: 0
Bucket [250.514448, 253.242371), Count: 0
Bucket [253.242371, 256.000000), Count: 0
Bucket [256.000000, 258.787657), Count: 0
Bucket [258.787657, 261.605670), Count: 0
Bucket [261.605670, 264.454369), Count: 1
Bucket [264.454369, 267.334088), Count: 0
Bucket [267.334088, 270.245166), Count: 0
Bucket [270.245166, 273.187943), Count: 0
Bucket [273.187943, 276.162764), Count: 0
Bucket [276.162764, 279.169980), Count: 1
Bucket [279.169980, 282.209941), Count: 0
Bucket [282.209941, 285.283006), Count: 0
Bucket [285.283006, 288.389534), Count: 0
Bucket [288.389534, 291.529890), Count: 0
Bucket [291.529890, 294.704443), Count: 0
Bucket [294.704443, 297.913564), Count: 0
Bucket [297.913564, 301.157630), Count: 0
Bucket [301.157630, 304.437021), Count: 0
Bucket [304.437021, 307.752123), Count: 0
Bucket [307.752123, 311.103324), Count: 0
Bucket [311.103324, 314.491017), Count: 0
Bucket [314.491017, 317.915600), Count: 0
Bucket [317.915600, 321.377474), Count: 0
Bucket [321.377474, 324.877045), Count: 0
Bucket [324.877045, 328.414724), Count: 0
Bucket [328.414724, 331.990926), Count: 0
Bucket [331.990926, 335.606070), Count: 0
Bucket [335.606070, 339.260581), Count: 0
Bucket [339.260581, 342.954886), Count: 0
Bucket [342.954886, 346.689420), Count: 1
Bucket [346.689420, 350.464620), Count: 0
Bucket [350.464620, 354.280930), Count: 0
Bucket [354.280930, 358.138796), Count: 1
Bucket [358.138796, 362.038672), Count: 0
Bucket [362.038672, 365.981015), Count: 0
Bucket [365.981015, 369.966287), Count: 0
Bucket [369.966287, 373.994955), Count: 0
Bucket [373.994955, 378.067493), Count: 0
Bucket [378.067493, 382.184378), Count: 0
Bucket [382.184378, 386.346093), Count: 0
Bucket [386.346093, 390.553127), Count: 0
Bucket [390.553127, 394.805971), Count: 0
Bucket [394.805971, 399.105126), Count: 0
Bucket [399.105126, 403.451096), Count: 0
Bucket [403.451096, 407.844391), Count: 0
Bucket [407.844391, 412.285525), Count: 0
Bucket [412.285525, 416.775020), Count: 0
Bucket [416.775020, 421.313402), Count: 0
Bucket [421.313402, 425.901205), Count: 0
Bucket [425.901205, 430.538965), Count: 0
Bucket [430.538965, 435.227227), Count: 0
Bucket [435.227227, 439.966540), Count: 0
Bucket [439.966540, 444.757462), Count: 0
Bucket [444.757462, 449.600553), Count: 0
Bucket [449.600553, 454.496382), Count: 0
Bucket [454.496382, 459.445523), Count: 0
Bucket [459.445523, 464.448557), Count: 0
Bucket [464.448557, 469.506070), Count: 1
Bucket [469.506070, 474.618656), Count: 0
Bucket [474.618656, 479.786914), Count: 0
Bucket [479.786914, 485.011451), Count: 0
Bucket [485.011451, 490.292880), Count: 0
Bucket [490.292880, 495.631819), Count: 0
Bucket [495.631819, 501.028896), Count: 0
Bucket [501.028896, 506.484743), Count: 0
Bucket [506.484743, 512.000000), Count: 0
Bucket [512.000000, 517.575314), Count: 0
Bucket [517.575314, 523.211340), Count: 1

[codecov]

Codecov Report

Merging #4337 (78ac7b4) into main (87a3313) will increase coverage by 0.02%.
The diff coverage is 54.71%.

❗ Current head 78ac7b4 differs from pull request most recent head d6cddeb. Consider uploading reports for the commit d6cddeb to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4337      +/-   ##
==========================================
+ Coverage   84.67%   84.70%   +0.02%     
==========================================
  Files         298      298              
  Lines       11937    11970      +33     
==========================================
+ Hits        10108    10139      +31     
- Misses       1829     1831       +2     

Impacted Files	Coverage Δ
...elemetry.Exporter.Console/ConsoleMetricExporter.cs	0.00% <0.00%> (ø)
...cs/Base2ExponentialBucketHistogramConfiguration.cs	83.33% <ø> (ø)
...tryProtocol/Implementation/MetricItemExtensions.cs	85.24% <96.42%> (+2.12%)	⬆️
...s.HttpListener/Internal/PrometheusSerializerExt.cs	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes