[PJRT][IFRT] Update PJRT, IFRT, and Py executable getters to return PjRtLayouts
[PJRT][IFRT] Update PJRT, IFRT, and Py executable getters to return PjRtLayouts

Also updates the PjRtLayout binding to use nanobind, so we're not
mixing nanobind methods with pybind return types.

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/tensorflow/tensorflow/pull/63954 from elfringham:fix_312_setuptools da09611b50c51fc7654e139a01ceceb4174fce89
