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 98.27%. Comparing base (bad8e72) to head (c5be5d9). Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #351   +/-   ##
=========================================
  Coverage     98.27%   98.27%           
  Complexity      222      222           
=========================================
  Files            19       19           
  Lines           695      695           
=========================================
  Hits            683      683           
  Misses           12       12           

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