test(postgresql): add schema resolution tests for ENUM/DOMAIN with builtin names

test(postgresql): add schema resolution tests for ENUM/DOMAIN with builtin names

Add comprehensive unit tests to verify schema resolution for ENUM and
DOMAIN types when their names conflict with PostgreSQL built-in types.

Covers scenarios:
* raises CompileError when no schema/default is provided
* works with explicit schema specified
* inherits schema from table definition
* inherits schema from metadata

Tests are parameterized via @testing.variation and applied to both ENUM
and DOMAIN. Also includes compiler tests for naming conflicts to ensure
consistent error handling and valid SQL generation.

Closes: #12761