http3: improve the client API

[marten-seemann]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 80.95238% with 28 lines in your changes missing coverage. Please review.

Project coverage is 84.49%. Comparing base (eaa879f) to head (fe5826c).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
http3/transport.go	78.02%	18 Missing and 2 partials ⚠️
http3/client.go	85.71%	5 Missing and 3 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4693   +/-   ##
=======================================
  Coverage   84.49%   84.49%           
=======================================
  Files         151      151           
  Lines       15044    15066   +22     
=======================================
+ Hits        12710    12729   +19     
- Misses       1802     1805    +3     
  Partials      532      532           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.