#24793 fix(python-fastapi): rebase #24098 onto master (relax path/query/header strict typing, #21905)

This PR rebases @goopher's #24098 onto current master. It does not change the original fix; it only resolves merge conflicts and keeps the behavior working against upstream refactors that landed after #24098.

Original problem (#21905): Pydantic strict types (StrictInt/StrictStr/StrictFloat) and Field(strict=True) disable string coercion. Path/query/header values always arrive as strings, so FastAPI rejected valid requests with 422 (int_type: Input should be a valid integer).

Original approach (from #24098):

• Path/query/header params emit coercible types (int/str/float) and omit strict=True.
• Body params and the Python client stay strict (JSON bodies carry real types).
• Strictness is a type (PydanticCoercibleType), selected by getPydanticParameterType(), not a boolean flag.

What this rebase had to reconcile with master:

• Keep #24141's centralized ConstraintApplier (do not restore inlined min/max/length constraints).
• Keep #24098's PydanticCoercibleType and FastAPI getPydanticParameterType() for path/query/header.
• Regenerated python-fastapi petstore samples with HEAD's current signature shape (Query(...) / alias= / trailing commas) and the relaxed types.

Fixes #21905
Supersedes / continues #24098 (credit: @goopher)

PR checklist

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  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

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  Commit all changed files.
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Summary by cubic

Fixes #21905 by relaxing strict Pydantic typing for python-fastapi path/query/header/cookie params, which previously rejected valid requests with 422 because wire-string values couldn't be coerced to StrictInt/StrictStr/StrictFloat.

Bug Fixes

• Path/query/header/cookie params now emit coercible int/str/float types without strict=True via a new PydanticCoercibleType; body params and the Python client keep strict types.
• Endpoint argument commas now stay on the parameter line; a trailing newline in the endpoint_argument_definition.mustache partial was making them wrap onto their own line.
• Rebased onto master while preserving the ConstraintApplier from #24141, with regenerated petstore samples and regression tests.