Moved getWellbeingPackage() from SystemApi to TestApi.

Changed PackageManager#getWellbeingPackage from System to Test API since
the related GTS using the API is now being built against the test sdk.

Bug: 119330345
Test: atest com.google.android.wellbeing.permissionpolicy.gts.WellbeingPermissionPolicyTest
Change-Id: Id80f52a327f3faa292e7c647cac2b1fa0e03275f
3 files changed