Cleanup omissions when adding app ID migration to PMS

Follow up after multiple changes for leaving sharedUserId

- Cleanup some messy APIs in DeletePackageHelper
- Remove the SharedUserSetting if no apps remains in the group
- Set PackageRemovedInfo.mRemovedAppId when UID is removed
- Always delete app data when app ID changes during a downgrade
- Fix locking in restoreDisabledSystemPackageLIF(...)

Test: Build + TH
Bug: 179284822
Change-Id: I40853a0894788ede6e0755984d463d2212ec9f09