The previous logic allowed for setting different ALPN
values depending on the QUIC version in use. This was
needed to set the draft ALPN value before publication of
the RFC.
Since the QUIC connection establishment process includes TLS handshake logic,
Connect and TLS handshake are called in the following order:
ConnectStart -> TLSHandshakeStart -> TLSHandshakeDone -> ConnectDone.
Notice: Wait100Continue not implemented as quic-go doesn't support handling
Expect: 100-continue.
* http3: rename RoundTripper to Transport
* http3: rename SingleDestinationRoundTripper to ClientConn
* http3: construct the ClientConn via Transport.NewClientConn
