New UserManager API to request quiet mode.

Adding new API to request the end of quiet mode without asking the user
for their credentials.

Bug: 145732320
Change-Id: I80f313d269d46400fdb21ef9265fa7c0c3b5c7d0
Test: atest 'com.android.cts.devicepolicy.QuietModeHostsideTest#testQuietMode_noCredentialRequest'