[PM] Add invisible label detection in Launcher apps

Add the detection to let the user can see the label correctly. If the
label of the activity is empty, use the label of the application. If
it is still empty, use the package name instead.

Test: atest LauncherActivityInfoTest
Test: atest CtsPackageManagerTestCases:LauncherAppsTest
Bug: 299586370
Bug: 309896458
Bug: 307309770
Change-Id: I7b28ffb0604a5f5211c18276a13da3ae49222775