Better options for choosing what to trace

[kazuho]

IIUC, h2o has two modes, identified by the special argument "quic." If set, it logs QUIC and HTTP events. If not, it logs HTTP events only. The limitation of the approach is that it is not capable of logging QUIC events only (therefore it cannot be used for tracing other applications using quicly). The other problem is that it does not trace TLS events.

I think that things would become clearer if there were three options to designate tracing at each layer. E.g., -H for HTTP-level tracing, -Q for QUIC level, -T for TLS-level.