Introduce 'EchoGetEventsForRevision' hook
Introduce 'EchoGetEventsForRevision' hook

Collect event data and allow modification by a hook.

This allows extensions to look at the events generated so far,
add more events, or remove events.

Bug: T276990
Change-Id: I60818d57552946857077dee93b0adb036621b791

wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo,wikimedia/mediawiki-extensions-Echo