The idle period is set to 5sec.
We now also ping every second since last activity.
This makes the quic.Connection less prone to being closed with
no network activity, since we send multiple pings per idle
period, and thus a single packet loss cannot cause the problem.
This addresses https://security.snyk.io/vuln/SNYK-GOLANG-GOPKGINYAMLV3-2841557
by updating yaml v3 to latest version.
It also stops using yaml v2 directly (we were using both v2 and v3 mixed).
We still rely on yaml v2 indirectly, via urfave cli, though.
Note that the security vulnerability does not affect v2.