Use the matching relay port when using TURN servers as STUN servers

PortConfiguration::GetRelayServerAddresses() checked whether a relay
config had a port with the requested protocol, but then returned the
address of the config's first port. For a config listing e.g. a TCP port
before a UDP one, STUN binding requests were sent over UDP to the TCP
address, so no srflx candidate was gathered from that server and
gathering completion was delayed until the requests timed out.

Return the addresses of all ports that match the protocol instead.
RelayServerConfigs created from RTCIceServer URLs have a single port, so
only configs built directly through the native API are affected.

Bug: webrtc:573252240
Change-Id: I260c0f0afc3ddf61b3f34163e2b3a5a257b7575d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/508721
Commit-Queue: Kacper Wasniowski <kwasniow@cisco.com>
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48911}