[Jetpack Content Migration Flow] Add Notifications Screen to the flow

[ovitrif]

Fixes Partially #17372 (doesn't disable notifications in WP which is wip in #17371 nor navigates to next step).

Depends on #17425 so that PR should be reviewed & merged first, then this one is ready for review.
The [Status] Not Ready for Merge label can be removed once the PR it depends on is merged.

This PR implements the UI for the notifications step in the WordPress to Jetpack migration flow.
It also adds crossfade transition between the migration flow screens.

🏁 All these changes are behind a temporary feature flag.

🔔 Notice: Once the feature flag is enabled the migration flow will always be presented. The Jetpack app build has to be uninstalled (or "Clear Data" should be done) in order to revert back to the normal functionality. Further development on the data layer will make sure the migration is not attempted again once it's successful. To be partially handled in #17406.

To test:

0. Open the Jetpack app & login
1. Go to Me → App Settings → Debug Settings
2. Enable the JetpackMigrationFlowFeatureConfig & restart the app.
3. Tap the Continue button on the "Welcome to Jetpack!" screen
   • Note: Temporarily the migration progress is simulated by showing for 2 seconds a processing state.
4. Expect to see the "Notifications now come from Jetpack" screen
   • The Continue button has no functionality in this PR, that's handled in #17440.

Previews

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Regression Notes

1. Potential unintended areas of impact
   None

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)
   None - PR adds only UI and UI state changes.

PR submission checklist:

• I have completed the Regression Notes.
• 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 these changes on WordPress by downloading wordpress-installable-build-pr17435-e7dd931.apk

	💡 Scan this QR code with your Android phone to download and install the APK directly on it.
	App	WordPress
	Build Flavor	Jalapeno
	Build Type	Debug
	Commit	e7dd931

Note: This installable build uses the JalapenoDebug build flavor, and does not support Google Login.

[wpmobilebot]

📲 You can test these changes on Jetpack by downloading jetpack-installable-build-pr17435-e7dd931.apk

	💡 Scan this QR code with your Android phone to download and install the APK directly on it.
	App	Jetpack
	Build Flavor	Jalapeno
	Build Type	Debug
	Commit	e7dd931

Note: This installable build uses the JalapenoDebug build flavor, and does not support Google Login.

[peril-wordpress-mobile]

	Warnings
⚠️	This PR is assigned to a milestone which is closing in less than 4 days Please, make sure to get it merged by then or assign it to a later expiring milestone

Generated by 🚫 dangerJS

[antonis]

Great work @ovitrif 👍
I've tested the app on a Pixel 5 (Android 13) both with the JETPACK_MIGRATION_FLOW true and false and everything worked as expected. The code changes also LGTM 🎉