[RFC] Op based annotation for external codegen

One interesting thing we can see here is that we start to introduce op-related attributes for specific pass(AnnotateCompiler).

It would be great to discuss the potential API design and namespacing.

For example, given that the AnnotateCompiler pass is special to the “dnnl”, it would be useful to keep some of the attributes local to dnnl.py and only makes use of set_attr and get_attr in op as a generic API.