Set input thread priority to RT - try 4

This reverts commit 52da71d4.

Reason for revert: camera was using its own stale copy of libprocessgroup, and now has revved up its version that includes the new parsing code. So this time the json file update should work OK.

Original description:

To improve input latency, set the critical input threads to RT priority.
This will use RT priority on AOSP devices by default. OEMs can still
choose to customize what "input policy" means for their device, which
may not necessarily mean RT.

For example, on device with multiple small / big cores, input task
affinity could be changed to prioritize big cores + higher CPU frequency
/ voltage, but still keep the standard / default input thread priority.

Note: there is an open issue where the thread priority is not remaining constant. See b/378761104.

Bug: 330719044
Bug: 378761104
Flag: com.android.input.flags.enable_input_policy_profile
Test: took perfetto trace and checked the priority on InputDispatcher
and InputReader threads.

Change-Id: I449be0eeeac989222f5deefa62615478bd65b968