feat: Navigate via folder tree

[Pytal]

Summary

• Resolves Implement a folder tree sidebar #15253

• Allow toggling folder tree

Split commits for easier reviewing :)

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[skjnldsv]

Comments to be addresses later 👍

Will address in a separate PR!

[skjnldsv]

Congrats 🎉 🎉 🎉

[nickvergessen]

The #[ApiRoute(verb: 'GET', url: '/api/v1/folder-tree')] takes down our server and makes browsers freeze.
Had to shortcut it with:

		return new JSONResponse([], Http::STATUS_INTERNAL_SERVER_ERROR, [], JSON_FORCE_OBJECT);

[frake65]

The #[ApiRoute(verb: 'GET', url: '/api/v1/folder-tree')] takes down our server and makes browsers freeze. Had to shortcut it with:

		return new JSONResponse([], Http::STATUS_INTERNAL_SERVER_ERROR, [], JSON_FORCE_OBJECT);

Finally this shortcut works for me.

What exactly should the code called in function "getFolderTree()" be doing? - Implement the new feature side bar?
Nice idea, but we would need a more performant implemetation for that feature - and probably another user toggle to have it turned on or off.
If it stays as expensive as the current implementation (at least for larger file trees), another solution could be to add the file tree asynchrosely and have the directory view in place instantly.

[Pytal]

We are working on optimizing this feature @frake65, though the page might be too unresponsive with very large trees there is an "Enable folder tree" checkbox located in the Files settings dialog which can be toggled per-user and will prevent the endpoint from being called completely

[frake65]

I did remove the shortcut and now I'm using the toggle switch. - Thank you for pointing me there!
Sorry to say, but this implementation seems to be still buggy to me - not only slow:

• From a users view point at this time I get a file tree, where folder names do not match the folders that they link to at all, but have random names (name of a random folder within the sub tree they are pointing to).
• What should be the order of the folder names by the way? - Alphabetically would be my first guess.
• minor but still wrong: the german tranlation is missing in file "l10n/de.js" and "l10n/de.json" - so the toggle is named in english language for me.

In my opinion probably this feature should be postponed