Performance optimization for edit monitor

Instead of log every edit event immediately when received the event,
cache the events and log the cached events in batch periodically. In
case when there are many edits events recieved in a short time (probably
due to non-human operation like repo sync), send an aggregated edit
event instead to prevent performance degrade.

Test: atest edit_monitor_test
Bug: 365617369
Change-Id: Ibe1613cf1e2eb37ebc5dfa5c029b990854fcf91e