fix(normalizer): restore behavior of clearing a oneOf if the schema content cannot currently be used by the generator

[Mattias-Sehlstedt]

Restores behavior of clearing a oneOf when running normalization normalizeOneOf as part of the SIMPLIFY_ONEOF_ANYOF rule.

The only case that currently is kept is when the oneOf only has const branches. Note that this case is not really relevant as of current, with the introduction of const parsing with #23869 (being part of rule SIMPLIFY_ONEOF_ANYOF_ENUM), which is processed before SIMPLIFY_ONEOF_ANYOF.

Would be good to get feedback from the original author, since it could be that #22571 looks to forward meta annotations from a oneOf that is not tied to const.

Fixes #24574

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Summary by cubic

Restores the normalizer to clear oneOf under SIMPLIFY_ONEOF_ANYOF when the generator can’t use its content, keeping it only when all branches are OAS 3.1 const for potential enum handling. Fixes #24574.

• Bug Fixes
  • Added clearOneOf() in OpenAPINormalizer to drop oneOf on integer/number/string schemas unless ModelUtils.isOneOfOfConsts() is true.
  • Implemented ModelUtils.isOneOfOfConsts() (OAS 3.1 only; all branches must have const).
  • Expanded tests: collapse differing string patterns (StringPatternsWithOneOf); preserve const-only oneOf when SIMPLIFY_ONEOF_ANYOF_ENUM is disabled; extracted option keys to constants.
  • Updated C# sample OpenAPI to include StringPatternsWithOneOf.

^{Written for commit 565c78b. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

_{Re-trigger cubic}

[JPPortier]

We can imagine a V32 will be created/supported at some point in the future.
And then onto V32, due to the logic, we will have same behavior as in V30 but different from V31 if no one remember this logic and update this source.

What do you about testing against not V30 ?
Then ready for next V32 without having to update this file.

(and thank you for the PR)