* [relay] Relay annotation and partitioning for codegen

* Add fusion unit test

* fix comments

* Update include/tvm/relay/attrs/annotation.h

Co-Authored-By: 雾雨魔理沙 <lolisa@marisa.moe>

* rebase

* remove annotation helper

* rebase again

Co-authored-by: Cody Yu <comaniac0422@gmail.com>
Co-authored-by: 雾雨魔理沙 <lolisa@marisa.moe>