WIP: Support MSC4333's base functionality

[turt2live]

MSC: matrix-org/matrix-spec-proposals#4333

This PR is incomplete, and makes bad decisions.

For usage in clients, like so: element-hq/element-web#30648

TODO:

• Don't manually create the MSC4332 event
• Don't manually create the MSC4333 event
• Update the MSC4333 event when the protected rooms change
• Prepopulate the default list on the ban command instead of assuming everyone's setups match mine

Signed-off-by: Travis Ralston <travisr@matrix.org>