"Applying" potential Copilot code review rules

[trask]

Hopefully this is reflective of the changes copilot code review will suggest after #2170.

Please comment either here or there if you have suggestions about the style-guide.md that was used to generate this PR.

This PR was generated by running this prompt module-by-module:

Make minimal changes to update {module} module to follow all of the recommendations in docs/style-guide.md. Ignore the @Nullable annotation usage section of the style guide.

I made very minor manual fixes to Copilot's work after the fact, including reverting adding final to public classes in the stable aws-xray module.

(I skipped the consistent-sampling module for now, will apply to that later)