Add ENUM column

[vjik]

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

Related to yiisoft/db#1107

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.68%. Comparing base (9f0ec01) to head (89af030).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #465      +/-   ##
============================================
+ Coverage     96.64%   96.68%   +0.04%     
- Complexity      409      412       +3     
============================================
  Files            66       66              
  Lines          1192     1207      +15     
============================================
+ Hits           1152     1167      +15     
  Misses           40       40              

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[Copilot]

Pull request overview

This PR adds support for PostgreSQL enumeration column types. It enables the framework to recognize and properly handle both native PostgreSQL ENUM types and check-constraint-based enumerations.

• Renames enum_values to values for consistency across the codebase
• Adds tryGetEnumValuesFromCheck() method to extract enum values from CHECK constraints using the ANY (ARRAY[...]) pattern
• Maps ColumnType::ENUM to varchar in the column definition builder

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tests/Column/EnumColumnTest.php	Adds PostgreSQL-specific enum column tests with native ENUM types and test cases to verify non-enum CHECK constraints are not misidentified
src/Schema.php	Renames enum_values field to values, adds logic to extract enum values from CHECK constraints via new tryGetEnumValuesFromCheck() method
src/Column/ColumnDefinitionBuilder.php	Maps ColumnType::ENUM to PostgreSQL varchar type for column definition generation
CHANGELOG.md	Documents the new enumeration column type support feature

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