Do more stuff w/o ImfLock in onFinishPackageChangesInternal()

With this CL

  InputMethodManagerService.MyPackageMonitor
          .onFinishPackageChangesInternal()

will start more potentially heavy weight tasks outside of ImfLock to
reduce lock contention.  Most importantly, we no longer acquire
ImfLock at all when there is no update in InputMethodMap. This should
drastically reduce the likelihood of lock contentions around
MyPackageMonitor.

Overall there should be no user perceivable behavior change.

Bug: 329703038
Bug: 343601565
Test: presubmit
Flag: EXEMPT refactor
Change-Id: If140d635dc4f462554c3324cef4dbf902aafc136