[CMake] Prefer third_party/pybind11 by default (#58951)
Summary:
To make build behaviour aligned with other third_party/ libraries,
introduce `USE_SYSTEM_PYBIND11 (https://github.com/pytorch/pytorch/commit/d55b25a633b7e2e6122becf6dbdf0528df6e8b13)` build option, which set to OFF by
default, which means PyTorch will be build with bundled pybind11 even if
other version is already installed locally.
Fixes https://github.com/pytorch/pytorch/issues/58750
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58951
Reviewed By: driazati
Differential Revision: D28690411
Pulled By: malfet
fbshipit-source-id: e56b5a8f2a23ee1834b2a6d3807f287149decf8c
