[Input] Default buttonmaps for keyboard and mouse

[garbear]

Description

This PR provides buttonmaps for the default keyboard and mouse controllers to allow for keyboard/mouse input without peripheral.joystick installed or enabled.

The first three commits are renames/refactors with no functional change.

The final commit provides the default buttonmaps, and includes test cases to make sure they are correct. The test cases actually caught a bug in the existing code where the left/right meta keys were swapped.

Motivation and context

When testing the keyboard and mouse added to the Player Viewer in #24406, I noticed that when peripheral.joystick was disabled, there was no keyboard/mouse input.

How has this been tested?

• Compiles successfully on Windows/Ubuntu/macOS.
• Two new test files were added, both pass tests.
• Brief runtime testing confirmed that keyboard/mouse work without peripheral.joystick.

Included in my latest round of test builds: https://github.com/garbear/xbmc/releases

What is the effect on users?

• Fixed keyboard/mouse input in game if peripheral.joystick isn't present

Screenshots (if appropriate):

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)

[garbear]

I rebased after merging #24501. This PR should be a lot more reviewable now, as it's now virtually entirely new code.

[garbear]

Planning on merging in 24 hrs if no comments. Jenkins build this please.