Eliminate Orca's xmodmap solution for managing caps and shift lock

From some preliminary investigation, it appears that we can eliminate the horribly complex, confusing, and buggy xmodmap code related to caps and shift lock being the Orca modifier.

Desktop environments allow end users to remap CapsLock to do something else. And it works regardless of whether the user is in Wayland or X11. We should be able to do the same.

• Create an OrcaModifierManager that callers can use to toggle caps lock and shift lock as needed.
• Create environment-specific ModifierManagers that know how to do the toggling for their environment.
• The OrcaModifierManager will have the smarts to know which it should use for the given environment.