add a generic Debug() function to the connection tracer

[marten-seemann]

This might not be the cleanest API, but we really need a way to get custom events into qlog / qvis, to facilitate debugging.

[codecov]

Codecov Report

Merging #2909 (ff1f433) into master (a76879c) will increase coverage by 1.07%.
The diff coverage is 90.91%.

@@            Coverage Diff             @@
##           master    #2909      +/-   ##
==========================================
+ Coverage   85.77%   86.85%   +1.07%     
==========================================
  Files         133      134       +1     
  Lines        9180    10090     +910     
==========================================
+ Hits         7874     8763     +889     
- Misses        958      967       +9     
- Partials      348      360      +12     

Impacted Files	Coverage Δ
logging/multiplex.go	97.44% <0.00%> (-2.56%)	⬇️
qlog/event.go	97.66% <100.00%> (+0.06%)	⬆️
qlog/qlog.go	95.67% <100.00%> (+0.10%)	⬆️
internal/handshake/aead.go	97.40% <0.00%> (-0.38%)	⬇️
internal/ackhandler/ackhandler.go	0.00% <0.00%> (ø)
conn_windows.go	60.00% <0.00%> (ø)
streams_map_incoming_generic.go	93.85% <0.00%> (+1.62%)	⬆️
internal/handshake/updatable_aead.go	98.31% <0.00%> (+2.06%)	⬆️
conn_id_manager.go	96.35% <0.00%> (+2.80%)	⬆️
packet_handler_map.go	77.37% <0.00%> (+4.35%)	⬆️
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update a76879c...ff1f433. Read the comment docs.