Extend contacts menu to show system address book users too

Is your feature request related to a problem? Please describe.

With https://github.com/nextcloud/contacts/pull/173 and https://github.com/nextcloud/server/pull/3233 we removed the system address book contacts from the contacts menu.

With https://github.com/nextcloud/server/issues/37797 we expose the system address book in contacts, adding them back makes sense (while still respecting share enumeration settings).

cc @jancborchardt

Describe the solution you'd like

Remove the filter in \OC\ContactsManager::search and \OCA\Contacts\ContactsMenu\Providers\DetailsProvider::process that remove the system contacts from showing up.

Add share enumeration filtering to the \OC\ContactsManager::search function to limit the available contacts to what is allowed by admins.

Also remove guest users (same as in the system address book code from https://github.com/nextcloud/server/issues/37797)

Describe alternatives you've considered

Leaving the contacts menu as is

Additional context

Follow up to https://github.com/nextcloud/server/issues/19575

Start by reading \OC\ContactsManager::search and \OCA\Contacts\ContactsMenu\Providers\DetailsProvider::process, along with the referenced system address book behavior. Trace how share enumeration settings and guest users are handled, then verify that permitted system address book users appear in the contacts menu while excluded users do not.