fix: minor issues in room list

- allow to discard focus of search field
- properly circle the search field's progress indicator
- always keep search sections visible in order to workaround annoying
  behavior: When quickly searching for a chat and one is fast at
clicking on a room, it often happens that server side results just drop
in at this moment and one clicks at the wrong item -> with a static
height as now set, this no longer happens.

Signed-off-by: TheOneWithTheBraid <the-one@with-the-braid.cf>

assets/l10n/intl_en.arb

@@ -1450,6 +1450,7 @@
     "type": "text",
     "placeholders": {}
   },
+  "noSearchResult": "No matching search results.",
   "moderator": "Moderator",
   "@moderator": {
     "type": "text",