Add support for TensorFlow 2.18

[psamanoelton]

Summary

• Update TensorFlow Quantum build to support TensorFlow 2.18.1.
• Align Eigen with TensorFlow 2.18.1’s pinned revision.
• Define essential requirements in requirements.in and use pip-compile to produce requirements.txt

Key changes

• WORKSPACE:
  • bump @org_tensorflow to 2.18.1
  • add lightweight alias repo (pypi_wheel & local_config_cuda) to satisfy TF’s @pypi_setuptools reference when rules_python generates @pypi__setuptools.
• requirements.in:
  • set of requirements needed for building TFQ and running test scripts
  • requirements.txt is produced by running pip-compile --upgrade --generate-hashes -o requirements.txt requirements.in
• tensorflow_quantum/python/differentiators/linear_combination.py:
  • Updated np.math to .math and importing math to properly handle numpy 2.0.2

Testing

• Linux/Ubuntu 22.04 (Docker), Python 3.10, 3.11 & 3.12, Bazelisk → Bazel 6.5.0
• bazel build ... release:build_pip_package succeeds
• Unit tests (scripts/test_all.sh & ./scripts/ci_validate_tutorials.sh) pass
• Wheel installs and imports with TF 2.18.1 + tf-keras 2.18, Cirq 1.5.0, NumPy 2.0.2

Notes

• This keeps TFQ on Keras 2 path; Keras 3 migration can be handled in a a future PR.
• This changes will help on the incoming upgrades to 2.20.

[mhucka]

Really fantastic to see NumPy 2 and Cirq 1.5 compatibility. I just have one question, about the Eigen commit change. Otherwise LGTM.

[mhucka]

The commit hash is changed, but the comment still refers to version 3.4.90. Does this commit still correspond to 3.4.90?