[Cleanup] Add missing #include. Remove useless ones.

This CL is the result of running include-what-you-use tool on part
of the code base (audio target and dependencies) plus manual fixes.

bug: webrtc:8311
Change-Id: I277d281ce943c3ecc1bd45fd8d83055931743604
Reviewed-on: https://webrtc-review.googlesource.com/c/106280
Commit-Queue: Yves Gerey <yvesg@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25311}
diff --git a/modules/audio_coding/neteq/audio_vector.h b/modules/audio_coding/neteq/audio_vector.h
index 825a3bc..d0db332 100644
--- a/modules/audio_coding/neteq/audio_vector.h
+++ b/modules/audio_coding/neteq/audio_vector.h
@@ -11,7 +11,8 @@
 #ifndef MODULES_AUDIO_CODING_NETEQ_AUDIO_VECTOR_H_
 #define MODULES_AUDIO_CODING_NETEQ_AUDIO_VECTOR_H_
 
-#include <string.h>  // Access to size_t.
+#include <string.h>
+#include <cstdint>
 #include <memory>
 
 #include "rtc_base/checks.h"