Fix StrictMode I/O violations

onBeforeUnlockUser now happens on a worker thread that allows I/O.
In addition to that STATE_RUNNING_UNLOCKING is only set after
onBeforeUnlockUser. Otherwise non-DBA processes would be able to start
before unlocking completes (causing b/68995913)

Recents are now loaded on a worker thread

Bug: 68872660
Bug: 68871386
Test: UserControllerTest
Test: Tested on marlin/walleye (+factory reset)
Test: create/start work profile. create/start guest user
Change-Id: I4694dfa0bd523de33f0e600f2db22d02610b535c