* 1.Break down CMake scripts to smaller libraries per-directory.
2. Move some transformations and interfaces to the right folder.
3. Fix minor merge failure of the patch renaming files to use LLVM convention.
* Link OMBuilder with OMONNXOps.
* 1. Update the src location of generated ONNX dialect definition.
2. Link OMONNXRewrite with OMONNXOps.
* Fix path to tablegen for add_onnx_mlir_dialect_doc.
* Update build script for onnx_mlir_transform.
* 1. Remove comment code.
2. onnx_mlir_attribute_promotion -> OMAttributePromotion.
* Name tablegen generated files with LLVM convention.
* Nit: reorder libraries to link against.
* Nit: Link against MLIR first.