SF: Update InputFlinger outside main thread

Avoids parceling data inside  main thread and hot path. Also
avoids any binder contention with one way binder calls. See
bug for more details.

Re landing with the following changes:
Don't discard input commands if input dispatcher is not
available. This can happen if system server crashes and
recovers. We want to keep input commands until
input dispatcher becomes available.

Bug: 206380308
Test: presubmit
Test: systrace
Test: flickertests
Test: health/microbench/display/microbench-test-suite
Change-Id: If0344abdeb28c8a409eb2f641c1e78d53e6f59b2