Allow bulk enabling/disabling experiments in groups

[theskinnyghost]

What?

Closes #334

Add controls to bulk enable / disable all features in an experiment group.

(Follow up from #379 which got (auto)closed when #376 got merged)

Testing Instructions

• Visit the AI settings page and verify the "Enable all" and "Disable all" buttons are shown at the end of each experiment group
• Clicking the "Enable all" button should enable all experiments within the group. If all experiments are already enabled, the button should be disabled.
• Clicking the "Disable all" button should disable all experiments within the group. If all experiments are already disabled, the button should be disabled.
• Settings should be auto-saved with a contextual snackbar message showing
• If the global AI toggle is disable, the bulk manage toggle should become disabled
• Run E2E tests: npm run test:e2e -- --grep "Plugin settings"

[github-actions]

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Co-authored-by: theskinnyghost <theskinnyghost@git.wordpress.org>
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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.75%. Comparing base (cf338eb) to head (aeff5b0).
⚠️ Report is 17 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #422   +/-   ##
==========================================
  Coverage      65.75%   65.75%           
  Complexity       763      763           
==========================================
  Files             53       53           
  Lines           3863     3863           
==========================================
  Hits            2540     2540           
  Misses          1323     1323           

Flag	Coverage Δ
unit	65.75% <ø> (ø)

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[jeffpaul]

Works well in my testing, thanks!