Implement the ability for user-defined type casting

[Tigrov]

Related PR

• https://github.com/yiisoft/db/pull/941

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌
Fixed issues

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.47%. Comparing base (fc7c12c) to head (eb271b6). Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #346   +/-   ##
=========================================
  Coverage     98.47%   98.47%           
  Complexity      330      330           
=========================================
  Files            21       21           
  Lines          1052     1052           
=========================================
  Hits           1036     1036           
  Misses           16       16           

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