Make ExtraICEPing send slightly fewer extras

This patch introduces a minor tweak to how often
the extra ice pings are sent.
- never send if non of the candidates is relay
- only send (extra) if it was more than 100ms
  since you sent a ping.

The motivation for this is that we measured
an regression of 0.05% in call setup success rate.

Bug: webrtc:10273
Change-Id: Icff36297d57030853a9ff8d4f74aaf6c84051d26
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132702
Reviewed-by: Jeroen de Borst <jeroendb@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27601}