Add new-syle YAML unparsed metric

[theyostalservice]

Resolves LINEAR JIRA

Depends on #12386 (Update: MERGED :-) )

Problem

We need to support new yaml specs for metrics in the new V2 semantic layer YAML, although there is a lot of overlap. This PR addresses creating the spec for the YAML itself.

Solution

I broke the unparsed metric class into a base class and two different sub-classes based for v1 and v2. I did the same thing for the tests for unparsed metrics. (Sharing a base class and test is especially reasonable in this case because they share validation logic.)

The design goal here is to DRY as much as possible while also making it reasonable to do maintenance on only one version of YAML at once (including eventually surgically removing the old YAML format one day).

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 or 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.

[github-actions]

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[theyostalservice]

• Add derived_semantics.entities to models #12401
• Parse metrics on models #12397
• Add Parsed class for new-style YAML Metric #12161
• Add Semantic entities to columns for new YAML #12395
• Add new-syle YAML unparsed metric #12157 👈 (View in Graphite)
• Parse dimensions defined on dbt columns into a semantic model #12386
• main

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.37%. Comparing base (a5ff83d) to head (d65cf65).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12157      +/-   ##
==========================================
- Coverage   91.40%   91.37%   -0.03%     
==========================================
  Files         203      203              
  Lines       25144    25207      +63     
==========================================
+ Hits        22982    23033      +51     
- Misses       2162     2174      +12     

Flag	Coverage Δ
integration	88.20% <100.00%> (-0.10%)	⬇️
unit	65.33% <83.75%> (+0.03%)	⬆️

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Components	Coverage Δ
Unit Tests	65.33% <83.75%> (+0.03%)	⬆️
Integration Tests	88.20% <100.00%> (-0.10%)	⬇️

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[github-actions]

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