Before we only did that, when we basically didn't have the key yet. But
since we usually get sent a RoomKey when a new message is sent after we
sign in, we were discarding, that those messages should usually now be
trusted.

fixes #1598

Can also be used to fix some corruption.

fixes #1499

fixes #622

fixes #1355

So far we haven't seen any reduction in issues about database
corruption, so presumably this is unrelated and the lag is annoying.

See also:
https://daniel.haxx.se/blog/2023/01/08/copyright-without-years/
https://hynek.me/til/copyright-years/

We need to block the migrations returning until the migrations are done.

Fixes #1258