qtls: only attempt 0-RTT resumption for 0-RTT enabled session tickets

[marten-seemann]

In specific, these lines would overwrite the EarlyData property from false to true, when doing session resumption using DialEarly (code from master):

quic-go/internal/qtls/client_session_cache.go

Lines 49 to 54 in 2d7ea37

	var earlyData bool
	// restore QUIC transport parameters and RTT stored in state.Extra
	if extra := findExtraData(state.Extra); extra != nil {
	earlyData = c.setData(extra)
	}
	state.EarlyData = earlyData

In addition to fixing that, we now also avoid saving the transport parameters into the session ticket for non-0-RTT tickets (code from this PR):

quic-go/internal/handshake/crypto_setup.go

Lines 320 to 324 in 3e984c1

	if earlyData {
	// only save the transport parameters for 0-RTT enabled session tickets
	return h.peerParams.MarshalForSessionTicket(b)
	}
	return b

[codecov]

Codecov Report

Attention: 17 lines in your changes are missing coverage. Please review.

Comparison is base (2d7ea37) 83.80% compared to head (dff19db) 83.87%.
Report is 5 commits behind head on master.

Files	Patch %	Lines
internal/qtls/go120.go	0.00%	9 Missing ⚠️
internal/handshake/crypto_setup.go	75.00%	5 Missing ⚠️
internal/qtls/client_session_cache.go	40.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4183      +/-   ##
==========================================
+ Coverage   83.80%   83.87%   +0.08%     
==========================================
  Files         150      150              
  Lines       15428    15532     +104     
==========================================
+ Hits        12928    13027      +99     
+ Misses       2003     1998       -5     
- Partials      497      507      +10     

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[sukunrt]

one minor comment.