make QUIC a default transport

[marten-seemann]

This means that we'll finally be able to set the QUIC version in go-libp2p as well.

[Stebalien]

1. Let's do a patch release with the new TCP transport first (and maybe get the yamux fix in?). Then we can put this in a major release.
2. We should probably get implement a Transport.Close that waits for the reuse's GC to finish go-libp2p-quic-transport#211 in first, if possible.

[marten-seemann]

Let's do a patch release with the new TCP transport first (and maybe get the yamux fix in?). Then we can put this in a major release.

Agreed, that was the plan anyway.

We should probably get implement a Transport.Close that waits for the reuse's GC to finish go-libp2p-quic-transport#211 in first, if possible.

CI on this PR seems even more flaky than before, I hope that this PR helps.