Add ban on Matrix side when virtualUser is banned

Add ban on Matrix side when virtualUser is banned.

We don't want a half-brain scenario with the offender still able to add discussion to the Matrix side that everyone there still has to deal with.

Dev notes

• Code where we ban the trouble user from the Matrix room when we receive user reports, modules/chat-reports/index.js#L178-201

• We also need to sync all of the existing bans to Matrix -> #2806