resolve gosec suggestion, use crypo package for randomness

[jsirianni]

Description of Changes

Resolves Gosec suggestion

[/home/jsirianni/go/src/github.com/observiq/stanza/operator/builtin/transformer/filter/filter.go:84] - G404 (CWE-338): Use of weak random number generator (math/rand instead of crypto/rand) (Confidence: MEDIUM, Severity: HIGH)
    83: 
  > 84: 	if !filtered || rand.Float64() > f.dropRatio {
    85: 		f.Write(ctx, entry)

Please check that the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• Add a changelog entry (for non-trivial bug fixes / features)
• CI passes

[djaglowski]

Log Files	Logs / Second	CPU Avg (%)	CPU Avg Δ (%)	Memory Avg (MB)	Memory Avg Δ (MB)
1	1000	1.6379282	+0.24136806	129.21364	+0.2909546
1	5000	4.948312	+0.068892	136.23087	-1.8080597
1	10000	10.155442	+0.5001049	141.74124	-4.5172424
1	50000	51.77696	-0.24132538	170.92699	-2.401413
1	100000	99.74889	+2.464981	230.38806	-12.485458
10	100	2.2586708	+0.18969154	130.50337	-4.074356
10	500	5.827721	-0.08597994	138.90167	+0.24960327
10	1000	11.3103695	-0.7933855	148.91473	+4.352371
10	5000	56.873768	+1.9514122	177.35426	+0.75242615
10	10000	110.56446	+8.687332	240.24272	+21.220764

[codecov]

Codecov Report

Merging #357 (7c3e2ae) into master (2113838) will increase coverage by 0.07%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master     #357      +/-   ##
==========================================
+ Coverage   69.37%   69.44%   +0.07%     
==========================================
  Files         123      123              
  Lines        6519     6525       +6     
==========================================
+ Hits         4522     4531       +9     
+ Misses       1515     1514       -1     
+ Partials      482      480       -2     

Impacted Files	Coverage Δ
operator/builtin/transformer/filter/filter.go	57.14% <75.00%> (+1.97%)	⬆️
operator/builtin/output/otlp/otlp.go	61.73% <0.00%> (-2.47%)	⬇️
operator/builtin/output/newrelic/newrelic.go	70.09% <0.00%> (-0.93%)	⬇️
operator/builtin/input/file/file.go	76.43% <0.00%> (+1.91%)	⬆️
operator/builtin/input/tcp/tcp.go	74.14% <0.00%> (+4.31%)	⬆️

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