http3: qlog sent and received GOAWAY frames

[marten-seemann]

Part of #4124.

[Copilot]

Pull Request Overview

This PR adds qlogging support for GOAWAY frames in HTTP/3, enabling proper logging and monitoring of connection closure events. This is part of a larger effort to enhance qlogging capabilities.

• Adds GoAwayFrame struct and encoding logic for qlogging GOAWAY frames
• Implements qlogging events for both frame creation and parsing in GOAWAY scenarios
• Adds test coverage for the new GoAwayFrame functionality

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
http3/server.go	Added qlogging of GOAWAY frame creation during server graceful shutdown
http3/qlog/frame.go	Implemented GoAwayFrame struct and its encoding method for qlog output
http3/qlog/frame_test.go	Added test coverage for GoAwayFrame encoding
http3/qlog/event.go	Added HasValues method to RawInfo and conditional raw data logging
http3/conn_test.go	Enhanced tests to verify GOAWAY frame qlogging functionality
http3/conn.go	Added qlogging of GOAWAY frame parsing in connection handler

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[codecov]

Codecov Report

❌ Patch coverage is 65.71429% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.08%. Comparing base (7796175) to head (0b91df2).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
http3/qlog/event.go	50.00%	4 Missing and 2 partials ⚠️
http3/server.go	0.00%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5376      +/-   ##
==========================================
+ Coverage   83.04%   83.08%   +0.03%     
==========================================
  Files         158      158              
  Lines       18963    18990      +27     
==========================================
+ Hits        15747    15776      +29     
+ Misses       2591     2589       -2     
  Partials      625      625              

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