Don't accept any locally known edits earlier than the last known server-side aggregated edit

[bwindels]

This will prevent riot showing the wrong content for an edit event if we have a later SSA edit. This does trigger element-hq/element-web#10290 when redacting the last edit but that is a lesser issue IMO, and needs fixing separately.

[turt2live]

unfortunate it raises a bug, but this seems like its very much in progress anyhow

[bwindels]

hmm, it's not super clear-cut which is the most important issue to solve here (where solving them both will be some work):

not seeing the correct content for an edited message when following a permalink
(under the condition that the last edit happened far enough ahead of the original event that it's not paged in when viewing the permalink)

versus

redacting the currently last edit doesn't update the content
(under the condition that there was a gappy sync when to original event was received)

Both edge cases, so fair to merge this.