Port user menu to Vue

[Pytal]

• For [BITV] User menu must be focus trapped #36201

Summary

Move PHP user menu markup to Vue wrapped by the focus trapped NcHeaderMenu component

Before	After

Requires

• Allow empty route for navigation entries #36449
• Allow settings navigation items with no route entry #36508

Related

• Upgrade @nextcloud/vue from 5.4.0 to 7.5.0 firstrunwizard#815
• Mount menu entry into Vue user menu firstrunwizard#816

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)

[Pytal]

/backport to stable25

[nickvergessen]

Not breaking the external sites app, if that is why my review was requested.
From the technical changes in this PR I'm the wrong person to judge

[juliusknorr]

Can we be fully sure that the UserMenu has already been rendered at this point? Otherwise this might need some way of handling to not end up with a menu without the profile link which might become hard to debug later on.

[Pytal]

Should be as this is only executed when UserMenu has been mounted and emits core:user-menu:mounted

This only works as long as apps/user_status/src/menu.js is loaded before core/src/components/UserMenu.js, but if UserMenu.js loads and emits core:user-menu:mounted before menu.js can subscribe to the event then it wouldn't

For this I adjusted the logic to handle both cases

[juliusknorr]

Just some smaller comments, but looks good otherwise 👍

[Pytal]

Rebased

[szaimen]

Tested together with nextcloud/firstrunwizard#816 and works now but didnt review the code.

(Looks like the internal server issue was somehow caused by the viewer app not being installed).