Room list service search results don't update after undelying data changes

[stefanceriu]

The ElementX integration tests revealed a strange behavior: the search results don't automatically update when the underlying list changes e.g. all_rooms grows in size after the search has been initiated.

I imagine this would cause problems in other situations as well e.g. lazily computed display names, leaving rooms when filtered on them etc.

The problem is easily reproducible by trying to search for an old room after resetting the caches.

Also related element-hq/element-x-ios#1203