fix: upgrade to quic-go/quic-go v0.55.0

Bumping quic-go/quic-go requires bumping golangci-lint.

The new golangci-lint shows several errors related to potential integer conversions and overflow. I have started fixing as many issues as possible without introducing any API changes.

This means that the golangci-lint pipeline will fail until we have fixed all the outstanding issues.

See !94 (merged).

Closes #78 (closed).