Allow arbitrary types in model creation by updating config in create_model

[coolbeevip]

Allow Pydantic models for toolkit outputs to use arbitrary_types_allowed=True in MCP/fastMCP

Fixes #1131

Motivation and Context

Without this change, registering toolkit functions with non-standard output types (e.g. third-party objects) leads to Pydantic schema generation errors.

How Has This Been Tested?

Tested by registering and calling toolkit functions returning non-standard types; tool registration and function invocation now work as expected.

Breaking Changes

No breaking changes.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context