[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}

rtc_base/strings/string_builder.cc

@@ -10,11 +10,11 @@
 
 #include "rtc_base/strings/string_builder.h"
 
-#include <stdarg.h>  // for va_end, va_list, va_start
-#include <cstring>   // for strlen
+#include <stdarg.h>
+#include <cstring>
 
-#include "rtc_base/checks.h"                // for FatalLogCall, RTC_DCHECK
-#include "rtc_base/numerics/safe_minmax.h"  // for SafeMin
+#include "rtc_base/checks.h"
+#include "rtc_base/numerics/safe_minmax.h"
 
 namespace rtc {