Implement message edition and deletion

[progval]

Specs:

• Message editing and deletion ircv3/ircv3-specifications#425

• https://matrix.org/docs/spec/client_server/r0.6.1#m-room-redaction

• MSC2676: Message editing matrix-org/matrix-spec-proposals#2676

• Matrix->IRC deletion

• IRC->Matrix deletion

• Matrix->IRC edition

• IRC->Matrix edition