feat: add connection slot manager

[bdraco]

See home-assistant/core#84331

[codecov]

Codecov Report

Base: 80.23% // Head: 82.00% // Increases project coverage by +1.76% 🎉

Coverage data is based on head (8686d82) compared to base (f22eb33).
Patch coverage: 83.90% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #80      +/-   ##
==========================================
+ Coverage   80.23%   82.00%   +1.76%     
==========================================
  Files           2        4       +2     
  Lines         334      428      +94     
  Branches       85      105      +20     
==========================================
+ Hits          268      351      +83     
- Misses         43       50       +7     
- Partials       23       27       +4     

Impacted Files	Coverage Δ
src/bleak_retry_connector/bluez.py	83.16% <83.16%> (ø)
src/bleak_retry_connector/__init__.py	83.17% <100.00%> (+1.26%)	⬆️
src/bleak_retry_connector/const.py	100.00% <100.00%> (ø)

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