New known constant DBT_ENGINE env var prefix

[QMalcolm]

resolves #294

Description

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
• 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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.88%. Comparing base (04c18bd) to head (d8a2082).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #295   +/-   ##
=======================================
  Coverage   71.87%   71.88%           
=======================================
  Files          52       52           
  Lines        3634     3635    +1     
=======================================
+ Hits         2612     2613    +1     
  Misses       1022     1022           

Flag	Coverage Δ
unit	71.88% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.