Android: Fix generic controllers in UI

[garbear]

Description

This PR fixes generic controllers in the UI (and in game) by adding generic keycodes to the Android joystick driver.

PR is:

• Commit 1 - code improvement (also present in #25176)
• Commit 2 - fix

Note that this only fixes truly "generic" controllers that Android has no buttonmaps for. The particular symptom is that they don't work in either the UI or in game. This doesn't affect generic controllers that work in the UI but not in games.

Motivation and context

Allows generic controllers, that Android doesn't have buttonmaps for, to be mapped in Kodi.

How has this been tested?

Tested as part of my RetroPlayer builds since January: https://github.com/garbear/xbmc/releases

At least one generic controller was reported fixed by this PR (don't have the link).

What is the effect on users?

• Fixed generic controllers on Android

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• Student submission (PR was done for educational purposes and will be treated as such)
• None of the above (please explain below)