Unify rtcp packet setters

Renamed setters in rtcp classes
from WithField to SetField
from WithItem to AddItem or SetItems
from From to SetSenderSsrc
from To to SetMediaSsrc
Some redundant or unsued setters removed.
Pass-by-const& replaced with pass-by-value when appropriate.

BUG=webrtc:5260

Review-Url: https://codereview.webrtc.org/2348623003
Cr-Commit-Position: refs/heads/master@{#14393}

webrtc/modules/rtp_rtcp/source/rtcp_packet/sdes.h

@@ -36,7 +36,7 @@ class Sdes : public RtcpPacket {
   // Parse assumes header is already parsed and validated.
   bool Parse(const CommonHeader& packet);
 
-  bool WithCName(uint32_t ssrc, const std::string& cname);
+  bool AddCName(uint32_t ssrc, std::string cname);
 
   const std::vector<Chunk>& chunks() const { return chunks_; }