Let users filter the list of times they were pinged by the current room

Sometimes when I'm trying to find when I was pinged, I have to go back in the ping list a ways. It would be easier if I could filter the list by the current room. This would be useful to anyone who gets pinged a lot or just needs to see higher up the list.

My suggestion would be to modify the new pane shown in the first screenshot from Element 1.7.7 to have a link called "Notifications from this room". That would bring up the existing window, but with only notifications from the current room shown. I also suggest in that window (current version shown in the second screenshot) having a checkbox which would turn on or off the filtering. My recommendation is to do both.

I really couldn't come up with other options.

**Additional context**

The issue names no files, tests, or entry points. Start by locating the current notification pane and ping list described in the screenshots, then determine how a current-room filter could connect them. Done means users can open notifications from the current room and enable or disable that filter in the existing window.

Written by the indexing model from the issue text.