Fix admin enable/disable of Bluetooth file sharing

This is an extremely partial fix for a mostly-broken feature. For
fully-managed devices, this fixes the toggle for the file sharing
option, by detecting which Bluetooth package should be used rather than
just guessing.

However, on work profiles, the file sharing option does not really work
anyway, it just infinitely loads. In addition, it is not correctly
disabled when Bluetooth stops, so the icon just remains but doesn't
do anything.

A full fix would add the enable/disable sequence for *work* UserHandles
to BluetoothOppManager, so the LAUNCHER_ACTIVITY is properly enabled and
disabled. In addition, it would fix the issue described in the linked
bug to prevent infinite loading (dedicated bug: b/112625123).

Tag: #stability
Ignore-AOSP-First: For T?
Bug: 237389774
Test: Manual, verifying the *badged* BT file sharing icon appears/disappears as needed

Change-Id: I070987bc884947246c372c65691c4866ebd1e7c7