[pm] revert mLock changes for compat seinfo

This partially reverts ag/16176950. Because we need to modify SeInfo, it
is not a read-only usage of PackageState.

BUG: 206662650
Test: atest com.android.cts.appcompat.CompatChangesSelinuxTest#testTargetSdkRAppIsInLatestDomainWithLatestOptin
Change-Id: I7260f7ef0c09669fe25f0313cc1517c56f4eaed8