Move the Rent-A-Codecâ„¢ from CodecOwner to CodecManager

Future CLs will move it even further down the stack.

BUG=webrtc:5028

Review URL: https://codereview.webrtc.org/1431103002

Cr-Original-Commit-Position: refs/heads/master@{#10580}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c95c366f5a894d18b836dd16afcaa629134b0cae
7 files changed