Use android-activity's show_soft_input to summon the keyboard.

[podusowski]

Is is a followup for #3787, which became stalled. Together with #3839, it should allow basic typing in Egui (and probably others) on Android.

As I understand, this approach might not be compatible in some Android version due to some bug in Android's Game SDK, however it does work for my Android 12, so I believe it a gain regardless. Also, android-activity seems like a better place to address this bug anyway.

• Tested on all platforms changed
• Added an entry to the changelog module if knowledge of this change could be valuable to users

Not applicable, I think:

• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

[kchibisov]

Could you update the set_ime_allowed platform specific docs moving Android to ios.