Refactored menus, player, and escape_capsule to utilize new system.
Actions defined in Godot project file with default bindings.
Player/Vehicles now react to actions and GameplayInput states instead of polling Input directly.
They respond to commands via `_handle_gameplay_command` and should not implement _unhandled_input directly.
Kept some debugging input handling code in `player.gd` for things like F3/F5/F4/PageUp/PageDown.
We may want to move much of this out of `player.gd` into something that handles the gamestate more generally.
scorpion21211-cmd