New action/event system for keybindings and other inputs

[falko17]

We should refactor both our keybinding system and the action system. It has several drawbacks at the moment, such that it doesn't generalize well across platforms, or that a certain key can only be used once, globally (even if it might only sometimes be queried).

Some existing ideas for this are collected in this Excalidraw session¹, or alternatively here as an image:

Footnotes

1. If this link doesn't work, you can also check here. ↩