Update test::CreateVideoStreams to use num_temporal_layers.

MultiCodecReceiveTest/VideoSendStreamTest:
Configure num_temporal_layers via VideoEncoderConfig (and remove
implementations of VideoStreamFactoryInterface used to override
the default num_temporal_layers configuration).

Bug: none
Change-Id: I9855245477fe3c6fe48d1a755d401d6a35a17c70
Reviewed-on: https://webrtc-review.googlesource.com/c/107301
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25302}
diff --git a/test/encoder_settings.cc b/test/encoder_settings.cc
index cab90df..bfbd2bd 100644
--- a/test/encoder_settings.cc
+++ b/test/encoder_settings.cc
@@ -62,10 +62,13 @@
               : DefaultVideoStreamFactory::kMaxBitratePerStream[i];
       target_bitrate_bps = std::min(max_bitrate_bps, target_bitrate_bps);
 
-      // Used configured framerate if set.
       if (stream.max_framerate > 0) {
         stream_settings[i].max_framerate = stream.max_framerate;
       }
+      if (stream.num_temporal_layers) {
+        RTC_DCHECK_GE(*stream.num_temporal_layers, 1);
+        stream_settings[i].num_temporal_layers = stream.num_temporal_layers;
+      }
     } else {
       max_bitrate_bps = std::min(
           bitrate_left_bps, DefaultVideoStreamFactory::kMaxBitratePerStream[i]);