Increase restore timeout for system agents

This change is motivated by b/161248425 where the restore times out before all
call logs can be restored by CallLogBackupAgent. The CL increases
restore time limit for agents running in the system process. See the
linked bug below for rationale as to why the change is limited to system
agents only.

Changes in the CL:
  * Split timeouts for restore session and agent restore into 2 separate
    values in BackupAgentTimeoutParameters, so that the latter can be
    changed independently.
  * Pass application UID to #getRestoreSessionTimeoutMillis() so that we
    adjust the return value  based on whether the agent is part of the system.

Bug: 170076589
Test: 1. atest BackupAgentTimeoutParametersTest
      2. Populate 7000 call log entries; run backup; clear call history;
         run restore and verify it fails without the change and succeeds
         with the change.
Change-Id: Id32e34973be380f7206cb9000ca95e6b76bbf8c0