[DISCUSS] TVM Unity Transition Docs Refactor

Thanks @Hzfengsy , very glad to know you would work on it, nice! I think we can take NVPTX backend as reference. Just only codegen kernel code only, and just codegen as simple .ptx as hand writing one. We may not need end2end solution for evaluation, just want to use TVM’s operator level DSL to write kerenel efficiently.