set the ALPN based on the QUIC version in the HTTP3 server

[marten-seemann]

No description provided.

[codecov]

Codecov Report

Merging #2847 into master will increase coverage by 0.03%.
The diff coverage is 72.09%.

@@            Coverage Diff             @@
##           master    #2847      +/-   ##
==========================================
+ Coverage   85.83%   85.86%   +0.03%     
==========================================
  Files         134      134              
  Lines        9036     9053      +17     
==========================================
+ Hits         7756     7773      +17     
- Misses        939      941       +2     
+ Partials      341      339       -2     

Impacted Files	Coverage Δ
session.go	77.24% <ø> (ø)
internal/handshake/crypto_setup.go	66.59% <33.33%> (-0.08%)	⬇️
http3/server.go	64.86% <86.67%> (+3.03%)	⬆️
http3/client.go	86.18% <100.00%> (ø)

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