perf(base): Stop setting up the FS for every basic auth request

[provokateurin]

• closes Basic auth requests always set up the filesystem #31357

One more time, we're gonna celebrate 🎵 ✌️ (last time, I promise 🤞)

Needs nextcloud/guests#1400 to not break the Guests app.
Nothing needed to change on the server side, it's the exact same changes as with the last PR.

[provokateurin]

/compile

[nickvergessen]

• Needs to get Talk integration tests executed as verification it's not breaking things again. See https://github.com/nextcloud/spreed/pull/15630/files for a sample PR how to do it.

[provokateurin]

@nickvergessen nextcloud/spreed#15777

[provokateurin]

Deck will also need a testing PR for this branch, as it relies on the same logic that is currently breaking Talk sharing tests (but I already have a solution): https://github.com/nextcloud/spreed/actions/runs/17404020365/job/49403633071?pr=15777

[provokateurin]

nextcloud/deck#7219

[provokateurin]

I ran all the failing Talk and Deck integration tests locally, but they all pass 🙈 I double checked that I'm really using the correct branches, but it was all as intended.

[provokateurin]

I think this PR could be unblocked by #57295, as I was stuck on the VerifyMountPointEvent last time 🎉

[susnux]

@provokateurin do we still need the cache mount then?

server/lib/private/Files/Mount/CacheMountProvider.php

Line 21 in 0a24ae5

class CacheMountProvider implements IMountProvider {

[provokateurin]

I'm not sure what you mean and how this is related 🤔