save the RTT in non-0-RTT session tickets

[tanghaowillow]

Save the RTT in non-0RTT session tickets.
Fixes #3853 for go 1.21.

[codecov]

Codecov Report

Merging #4042 (b727b88) into master (2797f85) will increase coverage by 0.18%.
Report is 11 commits behind head on master.
The diff coverage is 58.54%.

@@            Coverage Diff             @@
##           master    #4042      +/-   ##
==========================================
+ Coverage   83.29%   83.47%   +0.18%     
==========================================
  Files         147      147              
  Lines       14908    14904       -4     
==========================================
+ Hits        12417    12441      +24     
+ Misses       1990     1967      -23     
+ Partials      501      496       -5     

Files Changed	Coverage Δ
internal/qtls/go120.go	28.17% <0.00%> (ø)
internal/qtls/go121.go	56.84% <11.11%> (+1.74%)	⬆️
internal/handshake/crypto_setup.go	57.73% <73.33%> (+0.55%)	⬆️
internal/handshake/session_ticket.go	100.00% <100.00%> (ø)

... and 12 files with indirect coverage changes

[marten-seemann]

Should we add a check here that the entire ticket has been consumed (r.Len() == 0)?

[tanghaowillow]

I think maybe it is only needed for unmarshaling non-0-RTT session ticket. A 0-RTT session ticket is end with transport parameters and unmarshaling transport parameters from session ticket always consumes all bytes of the session ticket(extra bytes would either be ignored as unknwon parameter IDs or cause an EOF error).

[marten-seemann]

Looks good, just one small nit, and two suggestions how to improve the tests.

[marten-seemann]

Thanks for all your work @tanghaowillow!