[Cleanup] Add missing #include. Remove useless ones. IWYU part 2.

This is a follow-up to
https://webrtc-review.googlesource.com/c/src/+/106280.
This time the whole code base is covered.
Some files may have not been fixed though, whenever the IWYU tool
was breaking the build.

Bug: webrtc:8311
Change-Id: I2c31f552a87e887d33931d46e87b6208b1e483ef
Reviewed-on: https://webrtc-review.googlesource.com/c/111965
Commit-Queue: Yves Gerey <yvesg@google.com>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25830}
diff --git a/modules/video_coding/video_codec_initializer.cc b/modules/video_coding/video_codec_initializer.cc
index 885fa84..cd3f1d7 100644
--- a/modules/video_coding/video_codec_initializer.cc
+++ b/modules/video_coding/video_codec_initializer.cc
@@ -10,17 +10,19 @@
 
 #include "modules/video_coding/include/video_codec_initializer.h"
 
-#include "api/video/video_bitrate_allocator.h"
+#include <stdint.h>
+#include <string.h>
+#include <algorithm>
+
+#include "absl/types/optional.h"
+#include "api/video/video_bitrate_allocation.h"
 #include "api/video_codecs/video_encoder.h"
 #include "common_types.h"  // NOLINT(build/include)
 #include "modules/video_coding/codecs/vp9/svc_config.h"
-#include "modules/video_coding/codecs/vp9/svc_rate_allocator.h"
 #include "modules/video_coding/include/video_coding_defines.h"
-#include "modules/video_coding/utility/default_video_bitrate_allocator.h"
-#include "modules/video_coding/utility/simulcast_rate_allocator.h"
+#include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
-#include "rtc_base/system/fallthrough.h"
-#include "system_wrappers/include/clock.h"
+#include "rtc_base/scoped_ref_ptr.h"
 
 namespace webrtc {