Refactor modal

[JammingBen]

The current implementation of our modal has quite a few downsides, such as holding logic that it is not supposed to hold (e.g. password enforcement rules) and being limited to one active modal.

To-Dos

• Decouple modal from store and use a wrapper component that handles the modals (e.g. via event bus)
• Allow stacking multiple modals that will be processed in a queue
• Remove custom logic such as password enforcement rules and use dedicated components instead
• Clean up modal implementations where the logic is currently spread all over the place. These things should be file actions that create a modal using a custom component. Logic can then sit either in the file action, or in the component (see e.g. how it's done in feat: show modal when creating links in embed mode #10076).
  • Quota modal
  • Create user modal
  • Edit user login modal
  • Add/remove users to/from groups modal
  • Create group modal
  • Create shortcut modal
  • Readme content modal
• Establish pattern for onConfirm/onCancel handling
  • Establish clean pattern to replace the buttons while still leveraging the onConfirm handling
  • Close modal automatically when onConfirm successfully returns/resolves
  • Show progress indication while promise has not returned (and disable button)