Search searches "Display names" of rooms, but not their aliases

[spaetz]

Steps to reproduce

This is a rephrasing of #2762 which has a very vague title.

Join rooms, e.g. #element-x-android:matrix.org (Display name: Element X Android)

Hitting the search icon lets us search the 'Display names' of rooms, but not the aliases of a room

Outcome

If you type "element-x" no result will be shown. If you search "Element X", the room will be shown.

I would expect that a search finds rooms by alias for sure (and possibly by Display name).

Application version and app store

Element X 0.7.2 (and earlier)

Homeserver

Synapse 1.118