Merge to M76: Use the dummy address 0.0.0.0:9 in the c= and the m= lines if the default connection address is a hostname candidate.

Using a FQDN in the c= line has caused an inter-op issue with Firefox
when hostname candidates are the only candidates gathered when forming
the media sections. To address this issue, we use 0.0.0.0:9 when a
hostname candidate would be used to populate the c= and the m= lines.

The SDP grammar related to ICE candidates has been moved out of RFC8445,
and is currently defined in draft-ietf-mmusic-ice-sip-sdp. A FQDN
address must not be used in the connection address attribute per the
latest draft, if the ICE agent generates local candidates. Also, the
wildcard addresses  (0.0.0.0 or ::) with port 9 are given the exception
as the connection address that will not result in an ICE mismatch. We
thus adopt the aforementioned solution after combining these
considerations.

TBR=hta@webrtc.org

(cherry picked from commit 3ae59d33a310280e2f21ed4c53849950171e48e8)

Bug: chromium:927309, chromium:982108
Change-Id: I3df2db0f154276da39f99650289cf81baa677e74
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/145280
Commit-Queue: Qingsi Wang <qingsi@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Original-Commit-Position: refs/heads/master@{#28547}
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/145703
Reviewed-by: Seth Hampson <shampson@webrtc.org>
Cr-Commit-Position: refs/branch-heads/m76@{#3}
Cr-Branched-From: 57dc02a5c268548fde45f68a367d4d9920f82a17-refs/heads/master@{#28114}