Improve the code quality of the schema.column_type.ColumnType

[ahsimb]

1. No documentation at all. Does the name include the size and precision? God knows.
2. If the name is not the full name then the full_name property would be very helpful.
3. Consider implementing the __eq__ method for type comparison.

[ckunki]

See linked ticket in IntRef for details

[ckunki]

• ColumnType already has method eq, as marked with @dataclasses.dataclass(frozen=True, repr=True, eq=True), see also related tests.
• Instead of full_name (including type parameters, such as precision or size) I propose looking at property for_create of class Column and type.rendered, instead.