Fix missing ALTER ... SET DEFAULT for inherited columns in table SQL. (#9774)

When a table inherits a column from a parent, the generated table
SQL/EDIT script omitted the column's default. Emit a post-create
ALTER TABLE ... ALTER COLUMN ... SET DEFAULT for inherited columns
that carry a default, and show the default in the inherited-column
comment, across all version buckets.

Generated columns (colconstype 'g') are excluded from both the new
ALTER statement and the comment default, consistent with the inline
column-definition logic, since SET DEFAULT is invalid for a generated
column.