Add "Settings" context menu action

To test:

• Select "Settings" from Post (or Pages) context menu
• Verify that when you tap "Cancel", the changes settings are reset to the previous values
• Verify that when you dismiss the settings interactively, the changes settings are reset to the previous values
• Verify that when you tap "Done", the changes are saved after showing a spinner and temporarily disabling interactions

Regression Notes

1. Potential unintended areas of impact: Posts & Pages
2. What I did to test those areas of impact (or what existing automated tests I relied on): manual
3. What automated tests I added (or what prevented me from doing so): n/a

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

UI Changes testing checklist:

• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• VoiceOver.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• iPhone and iPad.
• Multi-tasking: Split view and Slide over. (iPad)