Add accessors to the types in the RTPVideoTypeHeader in RTPVideoHeader.

This CL is in preparation to change the RTPVideoTypeHeader into an absl::variant.

Bug: none
Change-Id: I1672d866df0395f3417d8e278cc67f017ab0ff98
Reviewed-on: https://webrtc-review.googlesource.com/87261
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23856}

modules/rtp_rtcp/source/rtp_format.h

@@ -26,7 +26,7 @@ class RtpPacketizer {
   static RtpPacketizer* Create(VideoCodecType type,
                                size_t max_payload_len,
                                size_t last_packet_reduction_len,
-                               const RTPVideoTypeHeader* rtp_type_header,
+                               const RTPVideoHeader* rtp_video_header,
                                FrameType frame_type);
 
   virtual ~RtpPacketizer() {}