Jetpack Focus: Remove Jetpack features during phase 4

[hassaanelgarem]

Part of #19810

Description

This PR partially removes the jetpack features for users in P4. It removes the tab bar and removes the visible entry points for Jetpack features.

This PR also disables Quick Start and the onboarding prompt for the simplified UI. It also removed the outdated My Site Dashboard feature flag.

⚠️ Disclaimer ⚠️

In the simplified UI, we no longer display a WPTabBarController. However, many areas of the app depend on WPTabBarController.sharedInstance to perform some actions. And for that, the simplified UI at this point has some known issues. One issue, for example, is that the Floating Button actions are not working.

These issues will be addressed in a following PR that removes all the dependencies on WPTabBarController.sharedInstance.

Screenshots

iPhone	iPad

Testing Instructions

1. Run the app
2. Open the debug menu and disable all the Jetpack Features Removal flags
3. Kill the app
4. Relaunch the app
5. Make sure the app is behaving normally
6. Open the debug menu and enable "Jetpack Features Removal Phase Four"
7. Kill the app
8. Relaunch the app
9. Make sure the tap bar is gone and all Jetpack features are removed.

Regression Notes

1. Potential unintended areas of impact
   N/A

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   N/A

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.

[wpmobilebot]

You can test the changes in Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr19816-c0ad158 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[wpmobilebot]

You can test the changes in WordPress from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr19816-c0ad158 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[staskus]

Leaving couple of comments, so far functionality worked as expected 👍

Moving on to check another PR since they are related.

[dvdchr]

Overall I think this looks good to me. I performed the testing steps on the iPad, and it works as described.

I'll check the second PR and verify that the floating button works.