Move frame_type member from RtpDepacketizer::ParsedPayload to RTPVideoHeader

The latter is also a member of the former. This cleanup is also
a preparation for dropping WebRtcRTPHeader::frameType (or deleting
WebRtcRTPHeader right away), now that it's a video-specific member.


Tbr: kwiberg@webrtc.org # Comment change in modules/include/
Bug: None
Change-Id: I5c1f3f981f0d750713fc9b9b145278150fe32b5d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/133024
Commit-Queue: Niels Moller <nisse@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27740}

video/buffered_frame_decryptor_unittest.cc

@@ -96,8 +96,9 @@ class BufferedFrameDecryptorTest
     VCMPacket packet;
     packet.video_header.codec = kVideoCodecGeneric;
     packet.seqNum = seq_num_;
-    packet.frameType = key_frame ? VideoFrameType::kVideoFrameKey
-                                 : VideoFrameType::kVideoFrameDelta;
+    packet.video_header.frame_type = key_frame
+                                         ? VideoFrameType::kVideoFrameKey
+                                         : VideoFrameType::kVideoFrameDelta;
     packet.generic_descriptor = RtpGenericFrameDescriptor();
     fake_packet_buffer_->InsertPacket(&packet);
     packet.seqNum = seq_num_;