PY: reduce Any in profile_helpers.py

[ryukzak]

Closes #177.

Investigated whether the ~40 Any in assets/api/writer-generator/python/profile_helpers.py could be meaningfully reduced. The count is dominated by intrinsic dict[str, Any] / Mapping[str, Any] value positions on untyped FHIR JSON, which are legitimately Any. Generics don't help: slice-getter inputs arrive via getattr(self._resource, ...) (typed Any), so any TypeVar collapses to Any and call-site cast()s remain.

The sound, non-cosmetic change is tightening "arbitrary input value" parameters from Any to object (Python's unknown) — only where the body already narrows via is_record / isinstance / hasattr, or just stores the value. This adds a mypy guardrail against un-narrowed access without any new casts or runtime change.

Changes

• Any → object on 19 parameters that accept an arbitrary dict / Pydantic-model / primitive:
  • Core helpers: is_record, _get_key, _model_get, matches_value (both params), is_extension, get_extension_value, extract_complex_extension, set_array_slice (value), set_array_slices (values)
  • Validation helpers: _get_field and all validate_* res params, plus validate_fixed_value expected
• Left as Any (cannot narrow soundly): push_extension / ensure_profile (assign attributes / call dict() directly on the param), all dict[str, Any] value positions (intrinsic FHIR data), and -> Any return types (tightening would just move casts to call sites).
• Regenerated the python-r4-us-core example (verbatim asset copy).

Before:

def matches_value(value: Any, match: Any) -> bool: ...
def validate_required(res: Any, profile_name: str, field: str) -> list[str]: ...

After:

def matches_value(value: object, match: object) -> bool: ...
def validate_required(res: object, profile_name: str, field: str) -> list[str]: ...

Verification

• make all passes (exit 0)
• Strict mypy on python-r4-us-core: no issues
• All Python and generator-snapshot tests pass; no snapshot drift