Add resolution alignment properties to RTCVideoEncoder protocol.

With this change, RTCVideoEncoder can specify:
- requested_resolution_alignment,
- apply_alignment_to_all_simulcast_layers
in the same way scaling_settings is specified.

Change-Id: I3de79a2eabaae581d6a9f2ef3e39496b9545a4f5

Bug: webrtc:12829
Change-Id: I3de79a2eabaae581d6a9f2ef3e39496b9545a4f5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/220933
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Abby Yeh <abbyyeh@webrtc.org>
Commit-Queue: Peter Hanspers <peterhanspers@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34196}

sdk/objc/components/video_codec/RTCVideoEncoderH264.mm

@@ -529,6 +529,14 @@ NSUInteger GetMaxSampleRate(const webrtc::H264ProfileLevelId &profile_level_id)
   return WEBRTC_VIDEO_CODEC_OK;
 }
 
+- (NSInteger)resolutionAlignment {
+  return 1;
+}
+
+- (BOOL)applyAlignmentToAllSimulcastLayers {
+  return NO;
+}
+
 #pragma mark - Private
 
 - (NSInteger)releaseEncoder {