Run unit tests only for plugins with changes

[ShyamGadde]

Summary

Fixes #1792

Relevant technical choices

• Run unit tests only for the plugin(s) affected by the changes in the pull request.
• Changes to the Optimization Detective plugin trigger tests for Embed Optimizer and Image Prioritizer due to their dependencies.
• All tests will run for all plugins when commits are added to the trunk branch.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.89%. Comparing base (d94977f) to head (fa1a433).

Additional details and impacted files

@@           Coverage Diff           @@
##            trunk    #1838   +/-   ##
=======================================
  Coverage   65.89%   65.89%           
=======================================
  Files          88       88           
  Lines        6878     6878           
=======================================
  Hits         4532     4532           
  Misses       2346     2346           

Flag	Coverage Δ
multisite	65.89% <ø> (ø)
single	38.58% <ø> (ø)

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