ColumnSchema classes for performance of typecasting

[Tigrov]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	✔️
Fixed issues	yiisoft/db#737

[what-the-diff]

PR Summary

• Deprecated Notice in ColumnSchema class
  Modifications to the ColumnSchema class now indicate that it's deprecated or phased out. The methods phpTypecast and dbTypecast in this class will continue to work for now but may be removed in future updates.

• Improved Testing in ColumnSchemaTest class
  Various changes have been made to the ColumnSchemaTest test class, making testing more robust. New types of columns are now tested, and the JsonColumnSchema class replaces the deprecated ColumnSchema class in certain tests. Plus, a new method tests whether the right column schema class is used for each column type.

• Added BigUnsigned Column in SchemaProvider class
  The SchemaProvider class now has a new column bigunsigned_col. This column can hold very large, positive whole number values, defaulting to 12345678901234567890.

• Changes in SchemaTest Test Class
  In the SchemaTest test class, new expectations for int_col have been established where it now expects the StringColumnSchema class instead of the older ColumnSchema.

• Addition in mysql.sql fixture file
  The mysql.sql fixture file now includes a new bigunsigned_col column in the type table. This column can hold large, unsigned integers, and it defaults to 12345678901234567890.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.25%. Comparing base (02685f0) to head (dbeea65).

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #303      +/-   ##
============================================
- Coverage     99.26%   99.25%   -0.02%     
+ Complexity      181      168      -13     
============================================
  Files            15       14       -1     
  Lines           547      534      -13     
============================================
- Hits            543      530      -13     
  Misses            4        4              

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