Extracted KnnIndexer class out of KnnGraphTester and moving to a knn package

[nitirajrathore]

In this PR

1. moved the current KnnGraphTester to knn package.
2. Extracted KnnIndexer class out of KnnGraphTester code so that the logic can be reused.
3. Extracted some more classes from KnnGraphTester to avoid bloating it as a coding best practice.

Tests :

ant build

python src/python/knnPerfTest.py

Also tested by passing the -indexPath to KnnGraphTester from knnPerfTest.py. Works fine.

Was able to run the command correctly and get output like

recall	avgCpuTime	numDocs	fanout	maxConn	beamWidth	totalVisited	reindexTimeMsec	selectivity	prefilter
0.971	0.71	10000	0	16	100	1339	7013	1.00	post-filter

[nitirajrathore]

Hi @msokolov : If you find time please review and help with merge.

[msokolov]

could you undo the output format change? I guess if markdown output is desired we could either post-process or add a command line option to control the format?

[msokolov]

I'm fine with e code re-org but would prefer to keep the output in TSV format so it can be consumed by other tooling

[nitirajrathore]

Sounds right. Will revert this part. My thought was that the output is generally pasted in the comments here so it would be better to pre-format it into md table.

[nitirajrathore]

I have reverted to csv format.

[msokolov]

sorry I lost track of this! merging now...

[benwtrent]

I am working on fixing this, as this breaks quantization, and adding options to quantize to 4bits.