Add a cache to parsing the host when encoding hosts

[bdraco]

What do these changes do?

Add a cache to parsing the host when encoding hosts

split out from #1188

We tend to parse the same hosts over and over again, so cache the parsing

Are there changes in behavior for the user?

no

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.59%. Comparing base (fe96599) to head (2581391).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1190   +/-   ##
=======================================
  Coverage   95.58%   95.59%           
=======================================
  Files          25       25           
  Lines        4871     4877    +6     
  Branches      259      260    +1     
=======================================
+ Hits         4656     4662    +6     
  Misses        189      189           
  Partials       26       26           

Flag	Coverage Δ
CI-GHA	95.57% <100.00%> (+<0.01%)	⬆️
MyPy	42.29% <100.00%> (+0.06%)	⬆️
OS-Linux	99.40% <100.00%> (+<0.01%)	⬆️
OS-Windows	99.48% <100.00%> (+<0.01%)	⬆️
OS-macOS	99.10% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	98.99% <100.00%> (+<0.01%)	⬆️
Py-3.10.15	99.28% <100.00%> (+<0.01%)	⬆️
Py-3.11.10	99.28% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	98.99% <100.00%> (+<0.01%)	⬆️
Py-3.12.7	99.28% <100.00%> (+<0.01%)	⬆️
Py-3.13.0	99.28% <100.00%> (+<0.01%)	⬆️
Py-3.8.10	98.94% <100.00%> (+<0.01%)	⬆️
Py-3.8.18	99.22% <100.00%> (+<0.01%)	⬆️
Py-3.9.13	98.94% <100.00%> (+<0.01%)	⬆️
Py-3.9.20	99.22% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.11	99.28% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.16	99.28% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.17	99.31% <100.00%> (+<0.01%)	⬆️
VM-macos-latest	99.10% <100.00%> (+<0.01%)	⬆️
VM-ubuntu-latest	99.40% <100.00%> (+<0.01%)	⬆️
VM-windows-latest	99.48% <100.00%> (+<0.01%)	⬆️
pytest	99.40% <100.00%> (+<0.01%)	⬆️

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