only Linux system is supported now.
change the default value of `ENABLE_AKG` to off, and controlled by option `-K`.
the `ENABLE_AKG` is auto enabled when `ENABLE_GPU` or `ENABLE_D` is on.
since now, we can use `ENABLE_AKG` to control the compilation of graphkernel
and akg codes.
fix usage description for option "-K", it should be "[-K on|off]".
LLVM is required by akg for cpu kernels, so AKG for cpu is default disabled now.
Add a subdirectory "model" in the "backend/optimizer/graph_kernel" for litegraph.
Implement two interfaces "AnfGraph2LiteGraph" and "LiteGraph2AnfGraph".
The litegraph will be the base data structure when we migrate the GraphKernel code
from python("mindspore/_extends/graph_kernel") to c++.
1. Update akg submodule
2. Refactor akg_kernel_build, akg_ascend_kernel_build, akg_gpu_kernel_build
3. Add akg_kernel_json_decoder to support converting kernel_json to AnfNode.
4. Add GraphKernel Cost Model. (mindspore/_extends/graph_kernel)
5. Add some GraphKernel passes to GpuSession, move these passes to backend/optimizer/graph_kernel.
6. Add global id for ir files.
7. Fix bug in ConstInputToAttr.