[pm] prevent changing sharedUserId after uninstall -k

ag/24750500 introduced a way to bypass the changing sharedUserId check
by using "-k" to uninstall a previously installed app. This CL fixes
that by shifting the check from fields of the old AndroidPackage object
to the fields of PackageSetting and SharedUserSetting.

BUG: 355334582
Test: manually by repeating the steps in the bug with an test app
Test: atest CtsSharedUserMigrationTestCases
FLAG: EXEMPT bug fix

Change-Id: Id53d632ea3d056c3bb5d293b32fa7e67c6076bfe