Exclude webcam and MIDI USB preferences from requiring auth challenge

Webcam / MIDI don't transfer any persistent data to the host device,
so it is okay to not guard it by an auth challenge. Auth challenge for
webcam use increases friction and reduces usability.

Bug: 349370229

Flag: com.android.settings.flags.exclude_webcam_auth_challenge

Test: Check when the flag is enabled, webcam / MIDI doesn't require auth
Test: Settings robolectric tests

Change-Id: Id4c97a635a4c0a9ed14f88fbdda2743e2371dd10
Signed-off-by: Jayant Chowdhary <jchowdhary@google.com>