Move PendingRequestPool and ParcelableUtils.

Move PendingRequestPool and ParcelableUtils to utils so that we could
reuse it for cpp VHAL client.
This CL also fixes a bug that the comment for PendingRequestPool
timeout unit is incorrect.

Test: atest VehicleHalVehicleUtilsTest
Bug: 214635003
Change-Id: Ie8ac1e0c4f49ae70caff7b680a7352fc23d4e680
7 files changed