Make the access check delegate thread safe

Add synchronization for the access check delegate state. Mutating state
and reading state is done under lock but executing implementations with
or without delegated uid/pkg are done outside of the lock.

Test: GtsRootDevicePolicyTestCases + permission CTS suites
Bug: 398808770
Bug: 394542184
Flag: EXEMPT test fix
Change-Id: I020e5e96833e0631b6b9c5a82b2f165d730e2e5b