Update minSdk to 24

[oguzkocer]

Fixes #15077 in combination with #15085 & #15138.

After an internal discussion, we decided to upgrade minSdk to 24 as we have less than 5% of our users on the earlier versions of Android.

I've also taken the opportunity to remove the versionName and versionCode values there were outdated.
Besides upgrading the minSdk, it removes obsolete checks for the earlier versions of sdk. I suggest turning on the hide whitespaces option to review these changes.

The only change that should be given extra attention to is 90ccc1a which merges values-v23 into values since these values will always be available. This is also what the lint task recommended to do.

Note that Automattic/stories-android#711 needs to be merged and the libs/stories-android submodule needs to be updated before this can be merged.

To test:

• Verify the app still works 🤷

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 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.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can test the changes on this Pull Request by downloading the APKs:

• Jetpack-pr-15135-build-113630.apk
• WordPress-pr-15135-build-113630.apk

[mokagio]

Makes sense to me, for the little understanding of Android that I have.

Looking at the diff without whitespace changes confirms that the code that was inside if statements hasn't been modified 👍

I run the app on the Emulator and posted a story because I saw that a few stories fragments did change. 🤷‍♂️