Fix setup_db.sh by waiting for pg_isready success return. Fixes #3876

[rvacaru]

resolves #3876

Description

The setup_db.sh script now waits for the postgres instance to be ready before terminating execution. Code for the creation of dbt database, root roles and grants on dbt has been removed since this is already done in the docker compose. The creation of role noaccess and db dbtMixedCase is kept.

Mind that I didn't successfully run make integration because I get an import error on all the tests on dbt.main. What I tested is that after the script ends I'm able to connect to postgres with:

• psql postgresql://root:password@localhost:5432/dbtMixedCase
• psql postgresql://root:password@localhost:5432/dbt

Checklist

• 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 updated the CHANGELOG.md and added information about my change to the "dbt next" section.

[kwigley]

forgive me while I close and reopen the PR to kick off the integration test workflow 🤦 , we are still working on a mechanism to re-trigger integration tests!

[rvacaru]

I rebased the branch with develop, that's why the forced push.

[jtcohen6]

@rvacaru Thanks for the contribution! The change itself looks good to me. I'm going to move your changelog note up to the topmost section, then we can merge this in :)