ActivityManager: Fix argument order for enqueueProcessChangeItemLocked

Change method arguments to be (pid, uid), the same as the callbacks.
The caller in OomAdjuster had the order wrong, and this change makes
that caller correct. The other caller in ActivityManagerService has been
changed as well.

Bug: 129074753
Bug: 129318739
Test: manual
Change-Id: Ifece49924a99ab592162f5b6466c7631d909408f