[PM-14476] Avoid multiple lookups in dictionaries (#4973)

* Avoid multiple lookups in dictionaries

* Consistency in fallback to empty CollectionIds

* Readability at the cost of lines changed

* Readability

* Changes after running dotnet format

src/Icons/Services/DomainMappingService.cs

@@ -13,9 +13,9 @@ public class DomainMappingService : IDomainMappingService
 
     public string MapDomain(string hostname)
     {
-        if (_map.ContainsKey(hostname))
+        if (_map.TryGetValue(hostname, out var mappedDomain))
         {
-            return _map[hostname];
+            return mappedDomain;
         }
 
         return hostname;