* Implement the virtual machine

Co-Authored-By: wweic <ipondering.weic@gmail.com>

* Fix rebase build issues

* Reorganize vm.py and fix allocator bug

* Remove compiler

* Remove tests

* Remove backend/vm/vm.cc too

* Fix docs

* Fix doc

* Fix doc

* Add vm docs

* Remove change to dead_code.cc

* Remove Relay logging

* Remove reduce

* Update include/tvm/runtime/vm.h

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Reformat

* Update include/tvm/runtime/vm.h

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Address feedback

* Update include/tvm/runtime/vm.h

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Apply suggestions from code review

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Fix a couple outstanding comments

* Last couple comments

* Update include/tvm/runtime/vm.h

Co-Authored-By: jroesch <roeschinc@gmail.com>

* Address code review feedback

* Fix final comment

* Address comments

* Error reporting and example

* add Const

* Explicitly delete copy assignment operator

* Fix rebase

* Pass 3rd arg to fusion