Update behavior deprecation flags to be behavior change flags

[mikealfare]

Description

Behavior changes are not always behavior deprecation changes. However, a lot of the verbiage and messaging around behavior flags suggested they only support deprecating changes. This PR updates this verbiage to allow for more types of behavior changes, e.g. changing how we do something (pg_catalog usage in dbt-redshift) or allowing users to opt-in to new features that will be fully supported in dbt as the data platform matures the feature (Iceberg usage in dbt-snowflake).

I'm adding Skip Changelog as the intent is already captured in a previous changelog; it would be duplicative.

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

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 25.42373% with 44 lines in your changes missing coverage. Please review.

Project coverage is 65.18%. Comparing base (9798ca7) to head (215fe50).

Files with missing lines	Patch %	Lines
dbt_common/events/types_pb2.py	2.22%	44 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #193      +/-   ##
==========================================
+ Coverage   65.16%   65.18%   +0.01%     
==========================================
  Files          52       52              
  Lines        3333     3323      -10     
==========================================
- Hits         2172     2166       -6     
+ Misses       1161     1157       -4     

Flag	Coverage Δ
unit	65.18% <25.42%> (+0.01%)	⬆️

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