Add constants for "SHORT_SERVICE" FGS

Bug: 257270313
Test: Manual inspection of `dumpsys activity settings`
Test: Run the following commands and then inspect `dumpsys activity settings` output
device_config put activity_manager deferred_fgs_notification_interval_for_short 1
device_config put activity_manager deferred_fgs_notification_exclusion_time_for_short 2
device_config put activity_manager short_fgs_timeout_duration 3
device_config put activity_manager short_fgs_anr_extra_wait_duration 4

Change-Id: I069b731a02e45c0a1f26609f2a8db444fdb03bb8