Remove per app language feature flag

[nbradbury]

This work-in-progress PR removes the per app language experimental feature flag, which enables AndroidX per app language handling for all users. This PR is so large because it also drops LocaleAwareActivity which was extended by dozens of activities.

[dangermattic]

	2 Warnings
⚠️	strings.xml files should only be updated on release branches, when the translations are downloaded by our automation.
⚠️	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

	1 Message
📖	This PR is still a Draft: some checks will be skipped.

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[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr21516-6e98d75
	Commit	6e98d75
	Direct Download	wordpress-prototype-build-pr21516-6e98d75.apk

Note: Google Login is not supported on these builds.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr21516-6e98d75
	Commit	6e98d75
	Direct Download	jetpack-prototype-build-pr21516-6e98d75.apk

Note: Google Login is not supported on these builds.

[sonarcloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud