Project issue: Unsupported blocks fallback mechanism

[guarani]

Description

Implement a fallback mechanism for unsupported blocks. A user who encounters an unsupported blocks should be able to view and edit the block in question, without leaving the mobile Gutenberg editor.

Required to ship to the public:

• [x] Enable unsupported block editing on dev builds
  • [x] Gutenberg PR
  • [x] Gutenberg Mobile PR
  • [x] WPAndroid PR
  • [x] WPiOS PR
  • [x] UI tests PR UI tests PR
• [x] Fix support for Atomic sites
• [x] Move resources to /rn-gutenberg-bridge(discussion).
• [x] Test with the monorepo branch
  • [x] Investigate reports of a "welcome to your site” screen shown while trying to edit an unsupported block (reported on Android)
• [x] Add basic usage track events
• [x] Fix the \n issue
• [x] Add test cases to manual test suite
• [x] Enable unsupported block editing on all builds

Extras:

• [x] Fix Auth issues after login
• [x] Handle the case when Gutenberg is disabled/unavailable on the backend (iOS, Android)
• [x] Unsupported Block Editor not working on sites where Jetpack is connected to WordPress.com
• [x] Increase tap-target of primary action on unsupported blocks https://github.com/wordpress-mobile/gutenberg-mobile/issues/2567
• [x] Unsupported block bottom sheet is triggered when device is rotated

To Dos:

• [ ] Enable the Unsupported Block Editor on Jetpack/Atomic sites where the Classic editor is the default
• [ ] Enable the Unsupported Block Editor on posts from self-hosted sites
• [ ] Improve the Unsupported Block Editor offline experience
• [ ] Make fallback option more discoverable (cog icon on block toolbar with options) cc @iamthomasbishop .
• [ ] Try fix WebView title for 3rd party blocks.
• [ ] Bottom sheet separators should go from side to side.
• [ ] (Android-only) Investigate report of keyboard popping up unexpectedly

Additional infomation

• Early discussion about project: https://github.com/wordpress-mobile/gutenberg-mobile/issues/1488

[etoledom]

We are finishing the focus on this feature after merging the main PRs (https://github.com/WordPress/gutenberg/pull/21150 https://github.com/WordPress/gutenberg/pull/25238) and the most important side PRs described on this ticket.

What's left will be worked later on after new assignments are made.