build: Enable macOS testing, upgrade zlib, add Python 3.13, and add .gitignore

[czgdp1807]

Description

This PR improves cross-platform support and build hygiene for the TensorFlow Metadata repository:

Changes

1. macOS CI Support: Enable continuous integration on macOS runners to catch platform-specific issues

   • Updated test.yml to run on both ubuntu-latest and macos-latest
   • Updated wheels.yml to build wheels on both Ubuntu and macOS platforms

2. Python 3.13 Support: Add Python 3.13 to test and wheel build matrices

   • Ensures compatibility with the latest Python version

3. Zlib Upgrade: Upgrade zlib from 1.2.12 to 1.3.1

   • Fixes macro conflicts and compilation issues on macOS with newer Clang versions
   • Resolves Apple Silicon compatibility issues (e.g., fdopen macro redefinition)

4. Repository Hygiene: Add .gitignore file

   • Excludes Bazel-generated directories (bazel-bin, bazel-metadata, bazel-out, bazel-testlogs)
   • Ignores generated protobuf Python files (*_pb2.py)
   • Prevents tensorflow_metadata.egg-info/ from being tracked

Motivation

• Support developers working on macOS and Apple Silicon systems
• Ensure the package builds cleanly on multiple platforms
• Reduce git repository noise from generated files
• Prepare for Python 3.13 adoption

Testing

• All CI workflows will run on both Ubuntu and macOS
• Wheels will be built for 8 configurations: 2 OS × 4 Python versions (3.9-3.12, 3.13)
• Local testing: pip install -e . and pytest should work on macOS after these changes

Related Issues

Fixes compilation issues on macOS Apple Silicon due to zlib/Clang compatibility.