Revert "Add spatial index to EncodedImage."

This reverts commit da0898dfae3b0a013ca8ad3828e9adfdc749748d.

Reason for revert: Broke downstream tests.

Original change's description:
> Add spatial index to EncodedImage.
> 
> Replaces the VP8 simulcast index and VP9 spatial index formely part of
> CodecSpecificInfo.
> 
> Bug: webrtc:9378
> Change-Id: I80eafd63fbdee0a25864338196a690628b4bd3d2
> Reviewed-on: https://webrtc-review.googlesource.com/83161
> Commit-Queue: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Erik Språng <sprang@webrtc.org>
> Reviewed-by: Sebastian Jansson <srte@webrtc.org>
> Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
> Reviewed-by: Philip Eliasson <philipel@webrtc.org>
> Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#24485}

TBR=brandtr@webrtc.org,magjed@webrtc.org,nisse@webrtc.org,sprang@webrtc.org,philipel@webrtc.org,srte@webrtc.org

Change-Id: Idb4fb9d72e5574d7353c631cb404a1311f3fd148
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9378
Reviewed-on: https://webrtc-review.googlesource.com/96664
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24486}
diff --git a/modules/video_coding/generic_encoder_unittest.cc b/modules/video_coding/generic_encoder_unittest.cc
index 2be6856..c889769 100644
--- a/modules/video_coding/generic_encoder_unittest.cc
+++ b/modules/video_coding/generic_encoder_unittest.cc
@@ -95,8 +95,8 @@
       image._length = FrameSize(min_frame_size, max_frame_size, s, i);
       image.capture_time_ms_ = current_timestamp;
       image.SetTimestamp(static_cast<uint32_t>(current_timestamp * 90));
-      image.SetSpatialIndex(s);
       codec_specific.codecType = kVideoCodecGeneric;
+      codec_specific.codecSpecific.generic.simulcast_idx = s;
       callback.OnEncodeStarted(static_cast<uint32_t>(current_timestamp * 90),
                                current_timestamp, s);
       if (dropped) {
@@ -189,6 +189,7 @@
   image.capture_time_ms_ = timestamp;
   image.SetTimestamp(static_cast<uint32_t>(timestamp * 90));
   codec_specific.codecType = kVideoCodecGeneric;
+  codec_specific.codecSpecific.generic.simulcast_idx = 0;
   FakeEncodedImageCallback sink;
   VCMEncodedFrameCallback callback(&sink, nullptr);
   VideoCodec::TimingFrameTriggerThresholds thresholds;
@@ -220,6 +221,7 @@
   image.capture_time_ms_ = timestamp;
   image.SetTimestamp(static_cast<uint32_t>(timestamp * 90));
   codec_specific.codecType = kVideoCodecGeneric;
+  codec_specific.codecSpecific.generic.simulcast_idx = 0;
   FakeEncodedImageCallback sink;
   VCMEncodedFrameCallback callback(&sink, nullptr);
   callback.SetInternalSource(true);
@@ -255,6 +257,7 @@
   const int64_t kTimestampMs3 = 47721860;
   const int64_t kTimestampMs4 = 47721870;
   codec_specific.codecType = kVideoCodecGeneric;
+  codec_specific.codecSpecific.generic.simulcast_idx = 0;
   FakeEncodedImageCallback sink;
   VCMEncodedFrameCallback callback(&sink, nullptr);
   // Any non-zero bitrate needed to be set before the first frame.
@@ -290,6 +293,7 @@
   CodecSpecificInfo codec_specific;
   const int64_t kTimestampMs = 123456;
   codec_specific.codecType = kVideoCodecGeneric;
+  codec_specific.codecSpecific.generic.simulcast_idx = 0;
   FakeEncodedImageCallback sink;
   VCMEncodedFrameCallback callback(&sink, nullptr);
   // Any non-zero bitrate needed to be set before the first frame.