Add in-app-update implementation

[jraska]

• Resolves Implement update API from Google Play #241

Implementation

• Basically follows https://developer.android.com/guide/playcore/in-app-updates only using abstractions like TopActivityProvider and SnackbarDisplay
• Flag used in_app_update_strategy with domain Flexible|Immediate|Off|empty string everything else triggers runtime non-fatal crash
• It is challenging to test this properly - so now no proper automation :shame

Notes

• When set download on Wifi, then the update available doesn't show for the next time.
• The isUpdateTypeAllowed() method is confusing. It is not controlled by Play Store as. I thought, but by type of update - for example when the update s downloaded only immediate update is available.

Visual

Config controlling if the app shoudl even check for updates - it adds as flexibility to target old versions, ccohorts or any other user group.

Flexible	Immediate	Update in progress

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[jraska]

This PR was released with 0.22.1