Add helper to query scalability structure configuration

without creating svc controller for it.

Bug: chromium:1187565
Change-Id: I219f88203e73036bf48bce04527bb8e46ccf1c33
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/231128
Reviewed-by: Johannes Kron <kron@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#34968}

modules/video_coding/svc/scalability_structure_simulcast.cc

@@ -65,6 +65,7 @@ ScalabilityStructureSimulcast::StreamConfig() const {
     result.scaling_factor_num[sid - 1] = 1;
     result.scaling_factor_den[sid - 1] = 2 * result.scaling_factor_den[sid];
   }
+  result.uses_reference_scaling = false;
   return result;
 }