[quic] add -v and -s to filter response headers

[gfx]

As discussed in #17, I'd like to add -v to enable send_response_header probe and -s to filter it (s comes from reSponse).

[toru]

Thank you for addressing the selective enable_probe issue. I left another comment that might be important.

[toru]

Is this condition what you really intended? My take is that this condition would allow HTTP-level send_response_header events to be printed even when -s foo is omitted. Would something like this make more sense?

if ev.type == "send_response_header":
    if allowed_res_header_name == None or ev.h2o_header_name != allowed_res_header_name:
        return

[toru]

One more thing, if we adopt the above condition, we'll no longer need the verbose option (at least for this round).

[gfx]

Oh, it has broken by 13146a8 and fixed in 320974b

My intention is:

• -v enables HTTP-level events (it might include receive_request_header in the future)
• If -v is specified and-s is omitted, all the HTTP-level events are printed
• if -v and -s are specified, only specified response headers

I think -v should exist if h2olog quic handles only quic tracing by default, but it can be removed if we do #21.

[toru]

I see your point. Thank you for the fix, and walking me through your reasoning. This makes sense to me. I also appreciate your flexibility:

but it can be removed if we do #21.

Agreed. There's no need to be fixated on that option if we do #21.

[toru]

LGTM. Thank you for addressing all the comments!