Support Android 12 (API 31)

[bmarty]

https://developer.android.com/about/versions/12

Things to do

Make the required changed

• Study all the changes from https://developer.android.com/about/versions/12/summary
• Migration recipe: https://developer.android.com/about/versions/12/migration
• Change compileSdk to 31
• Change targetSdk to 31
• Handle change in Bluetooth permission. Related: Update Bluetooth permissions to work with Android 12 and other small fixes #3901
• Handle change regarding deprecated API usage if any
• List to be continued (or to edit when implementing the required changes)
• Test the app on a Android 12 emulator
• Update / check the back press behavior https://developer.android.com/about/versions/12/behavior-changes-all#back-press
• Update the config to sign the APK here...
• ... and here

Effect

Making those change will allow some PRs to be merged, for instance #4241

To handle Later

All the possible changes to use new capabilities will be handled in dedicated issues.