Execute default expr when not dynamic.

[mathemancer]

Fixes #3716

This adds logic that executes the stored default expression for a column and then formats it properly for the given type whenever it's not dynamic.

Technical details

This should bring the current logic up to parity with the older behavior, or better. Since we now apply the format function to the default before putting it in the JSON for return, we (for example) return Date-type defaults in the same ISO format as the column values. The front end seems to happily consume this.

I modified a test to make sure the new behavior is working.

Note that when the default is dynamic (e.g., now() or GENERATED ALWAYS AS IDENTITY), we don't attempt to execute it. This is for a number of reasons, but the most important is that we don't want to burn sequence values when listing the columns of a table.

Screenshots

Before

After

Checklist

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• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
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  visible errors.

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[mathemancer]

@seancolsen I requested an optional review from you to make sure that:

• The behavior is as expected now from the API (I'm 90% sure it will be), and
• the formatting in the DB layer won't somehow mess up the front end logic (I'm less sure about that, but I did try a few different types and didn't notice any visible problems).

[seancolsen]

Works for me 👍🏻

[Anish9901]

Looks great!