bridgev2: Add way to process backfilled edits

[purpshell]

The situation

As of v0.21.0, the bridge is unable to handle message edits that happened in the past. Edits are not supposed to be in the message table. The network connector is unable to differentiate between a normal message and edit, which leaves all messages, edits and original in the table.

Suggested Solution

The current suggested solution is to process edits differently in FetchMessagesResponse. By adding a Edits property, and putting all edits in there, the network connector can drop "legacy"/non-infinite backfill messages containing edits without impacting the database.