Add a separate libtftrt.so shared library for TF-TRT which includes the trt

grappler optimizer, op kernels, and ops. This library will be included in pip
build, so users can use TF-TRT without building TF from source in C++.

This solves an issue mention by #23853 (TF-TRT not loadable with
TF_GraphImportGraphDef).

PiperOrigin-RevId: 238140294