shader: FMUL switch to using LUT (#3441)

* shader: add FmulPostFactor LUT table

* shader: FMUL apply LUT

* Update src/video_core/engines/shader_bytecode.h

Co-Authored-By: Mat M. <mathew1800@gmail.com>

* nit: mistype

* clang-format & add missing import

* shader: remove post factor LUT.

* shader: move post factor LUT to function and fix incorrect order.

* clang-format

* shader: FMUL: add static to post factor LUT

* nit: typo

Co-authored-by: Mat M. <mathew1800@gmail.com>