feat(marshmallow): support Tuple field in OpenAPI 3.1+ (closes #399)

[ansh-rohilla]

Summary

Implements support for marshmallow.fields.Tuple translation into OpenAPI 3.1+ schema definitions according to the JSON Schema 2020-12 standard (fixes #399).

Per discussion in #399:

• OpenAPI 3.1+ translates fields.Tuple into {"type": "array", "prefixItems": [...], "items": False}.
• If an older OpenAPI version (< 3.1.0) is used, an informative APISpecError is raised indicating that Tuple is only supported in OpenAPI 3.1.0 and above.
• In apispec.core.Components._resolve_refs_in_schema and SchemaResolver.resolve_schema_dict:
  • items resolution guards against boolean schemas (such as items: False) to prevent them from being incorrectly mutated into reference objects ({'$ref': '#/components/schemas/False'}).
  • Added recursive reference resolution for schemas within prefixItems.
• Registered marshmallow.fields.Tuple in DEFAULT_FIELD_MAPPING, _VALID_PROPERTIES, field2length, and added tuple2properties.

Testing

• Added comprehensive unit tests in tests/test_ext_marshmallow_field.py covering scalar fields, empty tuples, nullable tuples, Length validators, dump/load only, metadata, and nested tuples.
• Added integration tests in tests/test_ext_marshmallow.py testing schemas with tuples, nested schemas with references inside tuples, and operations with tuples validated against openapi-spec-validator.
• Added core ref resolution test in tests/test_core.py for OpenAPI 3.1 tuple schemas with prefixItems and items: False.
• All linters and test suites pass (pytest, mypy, ruff, pre-commit).