Add dataclasses to perf alert tool and refactor code.

[AnandInguva]

Fixes: #28395

Groups the variables in Dataclasses for better readability and extensibility

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[codecov]

Codecov Report

Merging #28889 (b312e05) into master (a3bf007) will decrease coverage by 0.07%.
Report is 2 commits behind head on master.
The diff coverage is 1.63%.

@@            Coverage Diff             @@
##           master   #28889      +/-   ##
==========================================
- Coverage   72.23%   72.16%   -0.07%     
==========================================
  Files         685      686       +1     
  Lines      101519   101551      +32     
==========================================
- Hits        73329    73286      -43     
- Misses      26612    26687      +75     
  Partials     1578     1578              

Flag	Coverage Δ
python	82.61% <1.63%> (-0.11%)	⬇️

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Files	Coverage Δ
...s/python/apache_beam/testing/analyzers/__init__.py	100.00% <100.00%> (ø)
...ache_beam/testing/analyzers/github_issues_utils.py	0.00% <0.00%> (-40.91%)	⬇️
...hon/apache_beam/testing/analyzers/perf_analysis.py	16.21% <0.00%> (-0.69%)	⬇️
...ache_beam/testing/analyzers/perf_analysis_utils.py	13.84% <0.00%> (-4.61%)	⬇️

... and 9 files with indirect coverage changes

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[liferoad]

Do we need to merge this PR to test whether it works or Performance alerting tool on Python load/performance/benchmark tests already tested it?

[AnandInguva]

This PR is just mostly refactoring. The unit tests tested the code. I tested the tool locally as well.

[liferoad]

LGTM. Please fix the precommit.