Support for custom MetricsFetcher in Perf tooling.

[AnandInguva]

Fixes: #28668

• Add MetricsFetcher class where anyone can inherit from it, build a Custom metrics_fetcher and pass it to the perf_analuysis.run()

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[codecov]

Codecov Report

Merging #28671 (5d35e4e) into master (e328ab5) will increase coverage by 0.24%.
Report is 70 commits behind head on master.
The diff coverage is 14.28%.

@@            Coverage Diff             @@
##           master   #28671      +/-   ##
==========================================
+ Coverage   71.96%   72.20%   +0.24%     
==========================================
  Files         680      684       +4     
  Lines      100172   101233    +1061     
==========================================
+ Hits        72088    73099    +1011     
- Misses      26509    26559      +50     
  Partials     1575     1575              

Flag	Coverage Δ
python	82.74% <14.28%> (+0.20%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...beam/testing/load_tests/load_test_metrics_utils.py	33.44% <ø> (-0.45%)	⬇️
...ache_beam/testing/analyzers/github_issues_utils.py	40.90% <28.57%> (-1.95%)	⬇️
...hon/apache_beam/testing/analyzers/perf_analysis.py	15.71% <11.11%> (-1.19%)	⬇️
...ache_beam/testing/analyzers/perf_analysis_utils.py	19.58% <10.52%> (-2.01%)	⬇️

... and 27 files with indirect coverage changes

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[AnandInguva]

R: @pranavbhandari24

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[AnandInguva]

@pranavbhandari24 any update?

[liferoad]

@Abacn @damondouglas FYI.

[pranavbhandari24]

Thanks Anand! Overall LGTM, just a couple concerns

[pranavbhandari24]

nit: only is repeated, we can omit it from the end of the sentence

[pranavbhandari24]

We had spoken about supporting multiple metric_name for a single test_id. These metric names will be provided as a list in the config.
Shouldn't we check if params['metric_name'] is a list and execute run_change_point_analysis for each metric_name?

[pranavbhandari24]

This can be done by adding metric_name as a parameter to run_change_point_analysis instead of accessing it directly in the method?

I'll defer to your opinion

[AnandInguva]

Yes, passing metrics as list will be implemented in a different PR. I will tag you there once it is ready.