[DO NOT MERGE] Add support for collections dict subclasses

[jrmccluskey]

Prototype for support for the dict subclasses in collections. Treats them as pure dictionaries for hint purposes, does not go further to validate the additional functions or set reasonable default types for bare cases (e.g. a bare Counter is treated as Dict[GenericKType, GenericVType] instead of Dict[GenericKType, int].)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.32%. Comparing base (5d38b8e) to head (9f03743).
Report is 194 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #34254   +/-   ##
=========================================
  Coverage     56.32%   56.32%           
  Complexity     3286     3286           
=========================================
  Files          1172     1172           
  Lines        178933   178944   +11     
  Branches       3398     3398           
=========================================
+ Hits         100778   100792   +14     
+ Misses        74898    74895    -3     
  Partials       3257     3257           

Flag	Coverage Δ
python	∅ <100.00%> (∅)

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[damccorm]

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[jrmccluskey]

These changes were pulled in as part of Mapping support, closing