Add warning_tag to UnversionedBreakingChange

[jtcohen6]

resolves #8827

Before

$ dbt ls -s state:modified --state state/
14:40:43  Running with dbt=1.7.0-b2
14:40:43  Registered adapter: postgres=1.7.0-b2
14:40:43  Found 2 models, 0 sources, 0 exposures, 0 metrics, 401 macros, 0 groups, 0 semantic models
14:40:43  Breaking change to contracted, unversioned model my_model (models/my_model.sql)
While comparing to previous project state, dbt detected a breaking change to an unversioned model.
  - Columns with data_type changes:
    - a_number (integer -> another)

my_dbt_project.my_model

After

$ dbt ls -s state:modified --state state/
14:41:38  Running with dbt=1.7.0-b2
14:41:39  Registered adapter: postgres=1.7.0-b2
14:41:39  Found 2 models, 0 sources, 0 exposures, 0 metrics, 401 macros, 0 groups, 0 semantic models
14:41:39  [WARNING]: Breaking change to contracted, unversioned model my_model (models/my_model.sql)
While comparing to previous project state, dbt detected a breaking change to an unversioned model.
  - Columns with data_type changes:
    - a_number (integer -> another)

my_dbt_project.my_model

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 lines are covered by tests ✅

Comparison is base (46ee3f3) 86.56% compared to head (66097c6) 86.44%.
Report is 17 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8828      +/-   ##
==========================================
- Coverage   86.56%   86.44%   -0.12%     
==========================================
  Files         176      176              
  Lines       25820    26043     +223     
==========================================
+ Hits        22350    22512     +162     
- Misses       3470     3531      +61     

Flag	Coverage Δ
integration	83.24% <100.00%> (-0.16%)	⬇️
unit	64.85% <100.00%> (-0.27%)	⬇️

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

Files	Coverage Δ
core/dbt/events/types.py	98.66% <100.00%> (+0.01%)	⬆️

... and 29 files with indirect coverage changes

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