[CPU/WebGPU] Support empty MatMulNBits weights - #33559

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: microsoft/onnxruntime-github-actions/setup-build-tools@d19341fb036c43a947a2c0e4a53ad4d15e10bc5c. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/