Implement alterColumn with expressionGenerated

[lbguilherme]

Description

Since PG17 it is possible to update the generated expression of a column. It should be supported on alterColumn.

https://www.postgresql.org/docs/17/sql-altertable.html

Suggested solution

pgm.alterColumn("tab", "col1", { expressionGenerated: "other + 1" });
pgm.alterColumn("tab", "col2", { expressionGenerated: null });

generates:

ALTER TABLE tab ALTER COLUMN col1 SET EXPRESSION AS (other + 1);
ALTER TABLE tab ALTER COLUMN col2 DROP EXPRESSION;

Alternative

No response

Additional context

No response