Improve Android 12+ splash images

### Description

The current behavior is that the splash screen is clipped on Android 12+. Previously, Android would just display the image as-is and you would have to do all the work yourself.

In Android 12, things got smarter and now the image is clipped inside a circle and you could potentially have a different foreground/background layer like the adaptive icons.

> https://developer.android.com/develop/ui/views/launch/splash-screen

### Public API Changes

None.

### Intended Use-Case

We could leverage the same properties of `` and do splash screens better. We can use the same logic to make adaptive icons, but just in the drawable folder and not generate the xml. Then the splash screen uses that drawable pair to make a nicer icon.

Start with the linked Android 12 splash-screen documentation and inspect the existing MauiIcon logic referenced in the issue. Trace how splash resources are generated in the drawable folder, then verify that Android 12+ can use separate foreground and background layers without clipping the image.

Written by the indexing model from the issue text.