Revert "[cleanup] Remove useless includes."

This reverts commit be8b5348c76105f8fe869b0cae4065ddca106419.

Reason for revert: Breaks downstream project

Original change's description:
> [cleanup] Remove useless includes.
> 
> Manual cleanup guided by include-what-you-use diagnostic.
> 
> Bug: webrtc:8311
> Change-Id: I00be03392cc7ee005101427ea7dc701621ccea68
> Reviewed-on: https://webrtc-review.googlesource.com/c/103320
> Commit-Queue: Yves Gerey <yvesg@webrtc.org>
> Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#25013}

TBR=phoglund@google.com,phoglund@webrtc.org,yvesg@webrtc.org

Change-Id: I7a6e1cdfef685173b76f234ad598083043dcd9a0
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:8311
Reviewed-on: https://webrtc-review.googlesource.com/c/104022
Reviewed-by: Oleh Prypin <oprypin@webrtc.org>
Commit-Queue: Oleh Prypin <oprypin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25015}

api/rtp_headers.h

@@ -13,7 +13,10 @@
 
 #include <stddef.h>
 #include <string.h>
+#include <string>
+#include <vector>
 
+#include "absl/types/optional.h"
 #include "api/array_view.h"
 #include "api/video/video_content_type.h"
 #include "api/video/video_frame_marking.h"
@@ -21,6 +24,8 @@
 #include "api/video/video_timing.h"
 
 #include "common_types.h"  // NOLINT(build/include)
+#include "rtc_base/checks.h"
+#include "rtc_base/deprecation.h"
 
 namespace webrtc {