Throttle checkForOptimize calls.

1. GetOptimizeInfo won't be called if it is within 4hrs from the last
time optimize runs.
2. Schedule GetOptimizeInfo with a delay, and won't
schedule it again if it has been already scheduled.

Bug: b/435251329
Flag: com.android.appsearch.flags.enable_throttling_check_optimize_info
Change-Id: Id98808976d2306522c33872986b504bad32e2f79