[DEBT] Move to fixtures better

[benfdking]

Can we move from these test types to using the fixtures with appropriate .sqruff files.

Rather than write a test for each configuration arrangement like currently done in postgres, we shoud just have a distinct .sqruff for each folder where we can specify each dialect configuration and then we can use the dialect fixture tests over all of the folders

Originally posted by @benfdking in #2404 (comment)