fix: get length attribute of postgres array columns

[edcolvin]

Description of change

Fixes #6990.

PostgresQueryRunner method loadTables is used to determine if the database is in sync with the entity definitions. This change updates how loadTables determines the length value of array columns. It uses the postgres-specific pg_catalog.pg_attribute table and the pg_catalog.format_type function to find the data type name, which includes the length for types that have a length attribute. Previously, loadTables relied solely on character_maximum_length in information_schema.columns, which is null for array columns. Because of this, array columns with a length attribute were always dropped.

This also includes a test that confirms the issues is resolved by this fix.

Pull-Request Checklist

• Code is up-to-date with the master branch
• npm run lint passes with this change
• npm run test passes with this change
• This pull request links relevant issues as Fixes #0000
• There are new or updated unit tests validating the change
• Documentation has been updated to reflect this change N/A
• The new commits follow conventions explained in [CONTRIBUTING.md]

[pleerock]

Thank you for the contribution!

It's super hard for me to review this kind of PRs because it's not possible to predict how these changes will actually work. Let's merge it and keep watching if it won't arise new issues.