Deprecate this package in favor of new framework

[jtcohen6]

Once our newer testing suite is available, we should redirect people to use that instead.

Blocked by:

• v1.1 final release
• Documentation: Initial docs for new adapter testing framework docs.getdbt.com#1263
• Packaging: [CT-313] Package new adapters tests dbt-core#4812

[nathaniel-may]

CT-383

[nathaniel-may]

@jtcohen6 what's the exit criteria for this ticket?

[jtcohen6]

@nathaniel-may At minimum, this repo should have a big "warning" sign in its README, redirecting people to use the new framework (link to docs). We should do the same for its predecessor: https://github.com/dbt-labs/dbt-integration-tests

We could take that a step further by:

• Flagging this package in PyPi metadata, by setting Development Status :: 7 - Inactive
• Archiving this repository