Support view on environment for commits and compare pages in rapid diffs

What does this MR do and why?

This MR adds "View on environment" (docs) to two pages in rapid diffs:

1. Commits page
2. Compare revision page

References

See implementation plan #554718 (comment 2857732295)

Screenshots or screen recordings

	Before	After
Commits Page
Compare Revision Page

How to set up and validate locally

Setting this up locally would involve quite a bit so I opted in to leverage existing features specs in spec/features/projects/view_on_env_spec

• adds live _debug to:
  • after line 62 wait_for_requests in when visiting the commit/'has a "View on env" button'
  • after line 121 wait_for_requests in when visiting the commit/'has a "View on env" button'
• enable feature flags:
  • rapid_diffs_on_compare_show
  • rapid_diffs_on_commit_show
• run bundle exec rspec spec/features/projects/view_on_env_spec.rb:115 for commits page or bundle exec rspec spec/features/projects/view_on_env_spec.rb:56 for compare page
• add ?rapid_diffs=true to the url

🗒️ for rapid diffs, this option is under a ellipse menu; for regular diffs, it's a icon button.

MR acceptance checklist

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Related to #554718