log when an old 1-RTT key is retired

[marten-seemann]

Depends on #2764.

[codecov]

Codecov Report

Merging #2765 into master will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2765      +/-   ##
==========================================
+ Coverage   86.60%   86.62%   +0.03%     
==========================================
  Files         128      128              
  Lines        9959     9979      +20     
==========================================
+ Hits         8624     8644      +20     
  Misses       1006     1006              
  Partials      329      329              

Impacted Files	Coverage Δ
internal/handshake/updatable_aead.go	94.62% <100.00%> (+0.08%)	⬆️
logging/multiplex.go	100.00% <100.00%> (ø)
qlog/event.go	96.17% <100.00%> (+0.06%)	⬆️
qlog/qlog.go	95.59% <100.00%> (+0.20%)	⬆️

---

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 9e1d65f...074f5a2. Read the comment docs.