posix tcp: use common refcnt implementation

[gdamore]

fixes #

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.07%. Comparing base (e3c017d) to head (013bb69).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2012      +/-   ##
==========================================
- Coverage   82.21%   82.07%   -0.14%     
==========================================
  Files          95       95              
  Lines       23896    23891       -5     
  Branches     3138     3137       -1     
==========================================
- Hits        19645    19608      -37     
- Misses       4177     4211      +34     
+ Partials       74       72       -2     

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