Nest Metric node meta under config

[QMalcolm]

Housekeeping

• I am a maintainer of dbt-core

Short description

The old/deprecated way of having meta was putting it directly on a node. However, awhile back we deprecated that paradigm and moved to nesting meta under a node's config. When revamped Metric nodes in 1.6, we forgot to move to the new meta paradigm, and thus Metric nodes have only been supporting the deprecated path. We need to ensure we support the desired path.

Acceptance criteria

• Metric nodes have a meta property under their config property
• During parsing, flat meta specifications should end up under the config.meta

Suggested Tests

• Metric meta can be specified in the dbt_project.yaml config specification
• In metric yaml, people can specify meta directly on a metric or under a metric's config, both should end up in a metrics config.meta

Impact to Other Teams

Change impacts Semantic Layer team (as they requested this).
Change impacts Artifacts team (change to the artifacts)

Will backports be required?

No

Context

No response