#7883274 Implement useSubscriptionManagerUserSettingsMutation

Closes #74433

Proposed Changes

This PR makes saving the UserSettings form possible. It adds:

• The mutation
• The button
• A notice component for success and error states

Testing Instructions

1. Apply this PR
2. Visit http://calypso.localhost:3000/subscriptions/settings
3. ⚠️⚠️⚠️ Clear your indexedDb from the Devtools & reload! Otherwise cached query data may still be present. ⚠️⚠️⚠️

3. Make some changes
4. Click the blue save button
5. You should get a notice that the settings are saved.

** Testing the error state **
Add an invalid input field in packages/subscription-manager/src/components/fields/EmailFormatInput/EmailFormatInput.tsx

<option value="invalid">{ translate( 'Invalid' ) }</option>

Try saving this value:

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the “[Status] String Freeze” label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the “[Status] Needs Privacy Updates” label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?