ci: Add comparison and visualization workflow for agent performance testing in CI

[nr-ahemsath]

Description

Implements #3308, adding the ability to run up to four performance tests with different agent versions (plus a no-agent baseline) and produce a summary table and charts for easy comparison of results.

Here is an example of the workflow, comparing the latest release (10.50.0) with the latest overnight all_solutions build (which should actually be identical, but this is just a demo): https://github.com/newrelic/newrelic-dotnet-agent/actions/runs/23308138260

Details:

1. The performance_tests.yml workflow (which ran a single performance test) was refactored into an action at .github/actions/run-perf-test/action.yml
2. compare_performance.yml is added to run up to four test scenarios, with the option to include a no-agent baseline (defaulting to true). Each run takes a label and a string which can be either an agent version number or a GitHub actions workflow run ID, which should be the run ID of an all_solutions.yml run from which to obtain the agent bits. If the input string is blank it defaults to the latest released agent version.
3. The charts are generated in a containerized ReportGenerator process that uses ScottPlot.
4. The output from each individual perf test has been made less verbose by default, and more human-readable.

There will be a follow-up PR or PRs which will do (at least) the following:

1. Make the nightly comparison compare current main with current release, instead of current release to no agent.
2. Enable convenient local performance test comparison runs.
3. Add a README.md that explains this whole system and how to use it.
4. Add the ability to configure the agent for each run with env vars, to enable more interesting performance comparisons.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.77%. Comparing base (1487c66) to head (853bfd3).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3496      +/-   ##
==========================================
- Coverage   81.79%   81.77%   -0.02%     
==========================================
  Files         508      508              
  Lines       34220    34220              
  Branches     4040     4040              
==========================================
- Hits        27990    27984       -6     
- Misses       5265     5269       +4     
- Partials      965      967       +2     

Flag	Coverage Δ
Agent	82.76% <ø> (-0.02%)	⬇️
Profiler	71.75% <ø> (ø)

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see 1 file with indirect coverage changes

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