make code ipv6 safe

[Luap99]

In many places strings.Split(remote, ":") is used to split the ip and port. This does not work for ipv6 addresses.

gvisor-tap-vsock/pkg/services/forwarder/ports.go

Lines 53 to 56 in 9d8e7a5

	split := strings.Split(remote, ":")
	if len(split) != 2 {
	return errors.New("invalid remote addr")
	}

To make this work with ipv6 addresses net.SplitHostPort should be used, https://pkg.go.dev/net#SplitHostPort.
To combine a port with a ip address use net.JoinHostPort, https://pkg.go.dev/net#JoinHostPort

[guillaumerose]

Very good point! ipv6 also deserves e2e tests I guess.