[Mobile] Going forward with mobile support for Android and iOS

[tebjan]

Copied from the Discussion on Discord:

The possible path forward:

Stride 4.0.x

• Recommend .NET 4.7.2 for iOS and Android development (should be working now with recent fixes)
• iOS and Android support will remain in a broken state on .NET 5.0 (this will not change)

Stride 4.1.x

• Support for net6.0-ios and .net6.0-android on .NET 6.0 (partly done, see comment by @xen2 below)

Miscellaneous

• Test the current state of OpenGL and OpenGL ES compatibility on Stride 4.0.x+ for iOS/Android

[xen2]

FYI, master (4.1) already has net6.0-ios (compiles, not tested) and net6.0-android (tested and it could run a default game; not sure if there might have been a bug with cubemaps (or not)).
So for sure 4.1 won't ship with .NET 5.0 (nor UWP). It's 100% .NET 6.0.

[tebjan]

related to: #1419