support meta at config level for metric nodes

[emmyoop]

resolves #9441

Problem

meta is not supported under configs for Metric nodes. It is only supported as the top level attribute. This is deprecated behavior and it needs to be supported at the config level.

Solution

Support meta at the config level while also maintaining backwards compatibility for meta at the metric level.

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
• This PR includes type annotations for new and modified functions

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2411f93) 87.97% compared to head (f10050a) 87.92%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9580      +/-   ##
==========================================
- Coverage   87.97%   87.92%   -0.06%     
==========================================
  Files         167      168       +1     
  Lines       22171    22211      +40     
==========================================
+ Hits        19506    19530      +24     
- Misses       2665     2681      +16     

Flag	Coverage Δ
integration	85.51% <100.00%> (-0.13%)	⬇️
unit	61.92% <60.00%> (+0.02%)	⬆️

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.

[QMalcolm]

This looks great! 🚀

[FishtownBuildBot]

Opened a new issue in dbt-labs/docs.getdbt.com: dbt-labs/docs.getdbt.com#4945