Update SendTimeHistory to store complete PacketInfo, not just send time

This will be used for the send side bitrate estimation. Storing various
meta-data about packets that can be retreived when arrival time feeback
arrives.

BUG=webrtc:4173

Review URL: https://codereview.webrtc.org/1288033008

Cr-Commit-Position: refs/heads/master@{#9859}
9 files changed