Update string logic for disabling MediaProjection single app option

Previously, the single app option for MediaProjection could only be disabled if there was an app name provided when building the dialog. Additionally, we only attempted to extract an app name if the requesting package didn't have cast permission. Now we always attempt to extract an app name (using the package name as a fallback), remove the condition of there being an app name to disabling the single app option and no longer rely on the app name being null to indicate if a package has cast permissions.

Bug: 329362311
Bug: 348323406
Flag: EXEMPT bugfix
Test: atest MediaProjectionPermissionDialogDelegateTest
Change-Id: Ica761c7145856ef7e701cc1fc6ef4c5e72938915