Support ext_type in the MsgPackPacket class

[miguelgrinberg]

Based on #1517, but using MsgPackPacket.configure() as method for configuring the ext type hooks.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b423d0e) to head (35edfad).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1521   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           31        31           
  Lines         2646      2656   +10     
  Branches       452       452           
=========================================
+ Hits          2646      2656   +10     

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