Fix Redshift vs view definitions

[jlrobins]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Unit tests are present
• Have you validated this change locally?

Summary of Changes

• Redshift dialect returns text() objects from get_view_definition(), surprising things and preventing encapsulation into pydantic message expecting exactly str. So capture and expliclty str() downgrade.

What is the Current Behavior?

• Cannot introspect Redshift databases that have views.

What is the New Behavior?

• Introspection succeeds.

[jlrobins]

Sketch in-notebook of the fix is over at https://app.noteable-integration.us/f/428e8a16-4997-4894-ad88-727f8ec77f9c/Redshift.ipynb . W/o the hooking in of custom get_view_definition(), the \introspect in that notebook fails.