* [REFACTOR][PY] Establish tvm.runtime

This PR establishes the tvm.runtime namespace that contains the core runtime data structures.
The top-level API are kept inact for now via re-exporting.

We will followup later to cleanup some of the top-level APIs.

* Fix ndarray name

* [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>

* add checkpoint annotation for checkpointing memory optimization

* add alpha-equivalence checkpoint test and fix gradient type issue

* fix build issues

* ignore checkpoint annotation when checking missing gradients

* refactor, fix checkpoint compute for tuple and add tests

* [HEADER] ASF header dir=include

* [HEADER] ASF Header dir=src

* [HEADER] ASF Header -dir=python

* [HEADER] ASF header dir=topi

* [HEADER] ASF Header dir=nnvm

* [HEADER] ASF Header -dir=tutorials

* [HEADER] ASF Header dir=tests

* [HEADER] ASF Header -dir=docker

* fix whitespace

* [HEADER] ASF Header -dir=jvm

* [HEADER] ASF Header -dir=web

* [HEADER] ASF Header --dir=apps

* [HEADER] ASF Header --dir=vta

* [HEADER] ASF Header -dir=go

* temp

* [HEADER] ASF Header --dir=rust

* [HEADER] Add ASF Header --dir=cmake

* [HEADER] ASF Header --dir=docs

* [HEADER] Header for Jenkinsfile

* [HEADER] ASF Header to toml and md

* [HEADER] ASF Header to gradle

* Finalize rat cleanup

* Fix permission

* Fix java test

* temporary remove nnvm onnx test