never keep track of more than 500 ACK ranges

[marten-seemann]

Fixes #2010. Builds on top of #2028.

[codecov-io]

Codecov Report

Merging #2029 into master will decrease coverage by 0.06%.
The diff coverage is 95.45%.

@@            Coverage Diff             @@
##           master    #2029      +/-   ##
==========================================
- Coverage   85.43%   85.37%   -0.06%     
==========================================
  Files          99       99              
  Lines        7174     7197      +23     
==========================================
+ Hits         6129     6144      +15     
- Misses        761      767       +6     
- Partials      284      286       +2

Impacted Files	Coverage Δ
session.go	72.09% <100%> (+0.13%)	⬆️
internal/ackhandler/received_packet_history.go	96.97% <100%> (+0.14%)	⬆️
internal/ackhandler/received_packet_tracker.go	79.55% <100%> (-0.45%)	⬇️
internal/ackhandler/received_packet_handler.go	63.27% <80%> (ø)	⬆️
internal/handshake/qtls.go	89.47% <0%> (-1.32%)	⬇️
internal/handshake/crypto_setup.go	67.42% <0%> (-1.12%)	⬇️
internal/ackhandler/sent_packet_handler.go	75.32% <0%> (+0.39%)	⬆️

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