refactor(keybindings): transition to native Mutter intercept and SRP …

[KonstantinMerkel]

Implements better keyboard shortcut architecture.

Behavioural Changes:

1. Should prioritise this extensions shortcuts over system defaults (may disable those while extension in use)
2. Should perfectly reenable those shortcuts on disabling of the extention. Should also be resilient against shell chrashes

Internal Changes:
Two methods used:

• For some default keys we hijack the executed code. High priority. But not always possible.
• For most we register new keys and shadow the old ones. Reenable on disable.