Fix the renamed relations code against 1.8

[VersusFacit]

resolves #693
docs dbt-labs/docs.getdbt.com/#

Problem

There are too many BEGINs and COMMITs in the logs. This is due to how we're nesting macros. This is a problem when drops and renames need to operate together in a single transaction.

This is a red herring. The real problem is renamed_relations is not evaluating right on instantiation and causing drops where there shouldn't be any.

Solution

Change instantiation semantics in core and here. Add test.

Checklist

• I have read the contributing guide and understand what's expected of me
• 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
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

[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]

This looks like it might be a dupe. I'll come back after merging the other PR and clean this up if that's the case.

[mikealfare]

After fixing rename_relations, this PR has been reduced to the changelog, hence I'm closing it as a dupe. Please refer to dbt-labs/dbt-core#9681 for more information.