ADAP-389: Stub materialized view as a materialization

[mikealfare]

resolves dbt-labs/dbt-core#6911

Description

Stub out the materialized view materialization for Redshift. Under the hood this just creates a view for now. But this can be used to verify all of the plumbing.

While creating the materialization, it was observed that other materialization templates existed outside of the materialization directory. These were moved from adapters.sql into the materialization directory in the appropriate file (e.g. table.sql). Some of the macros were also refactored to be smaller bits of code and dbt-postgres dependencies were eliminated when found.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the dbt-redshift contributing guide.

[mikealfare]

I'm skipping the change log on this; it's too granular. There will be a changelog at the feature level that will be merged into main.

[mikealfare]

I'm running into an issue while trying to recreate materialized views. They don't appear to show up as expected in pg_depend. When a materialized view is created, call it my_mat_view, based on a table called my_table, Redshift actually creates a view called my_mat_view and a table called tbl_mv__my_mat_view__0. The entries that show up in pg_depend tie my_mat_view to tbl_mv__my_mat_view__0, which is technically correct. Unfortunately, my_table does not show up at all even though that is the actual dependency from the user's perspective. I believe when we recreate the materialized view, we are inadvertently dropping it because the dependency is not properly managed when recreating the table.