feat: Introduce Python-side TypeInfo Metadata

[junrushao]

Previously, TypeInfo stays strictly in C and is glued to Python via Cython. This PR makes it Cython side registry to store Python objects, i.e. TypeInfo, which makes it possible to lookup type info in pure Python.

This PR is split from #8.

[Copilot]

Pull Request Overview

This PR introduces Python-side TypeInfo metadata to enable type information lookup in pure Python. Previously, TypeInfo was strictly maintained in C and accessed via Cython, but this change creates a Cython-side registry to store Python objects.

Key changes:

• Replaced C-only type registration with Python-accessible TypeInfo objects
• Moved class attribute reflection logic from Cython to Python for better maintainability
• Created new TypeInfo, TypeField, and TypeMethod data classes for structured metadata

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
python/tvm_ffi/_core_base.py	Introduces new TypeInfo, TypeField, and TypeMethod data classes for storing type metadata
python/tvm_ffi/registry.py	Moves class attribute addition logic from Cython and updates object registration to use TypeInfo
python/tvm_ffi/cython/object.pxi	Replaces simple class list with TypeInfo registry and creates TypeInfo objects from C metadata
python/tvm_ffi/cython/function.pxi	Removes old reflection-based class attribute addition logic
python/tvm_ffi/core.pyi	Updates type annotations to reflect new TypeInfo-based registration

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