Auto TensorCore CodeGen (#4234)

Auto TensorCore CodeGen (#4234)

* Add Auto TensorCore TensorCore Unit Test

* Rebase to tvm master branch & Add auto tensor core

* Code Refine

* Add tensor core switch by pragma

* Add pragma in tensor core example code

* Get real tile size to replace hard coded 16

* support more than 2 dimensions (e.g. batchmatmul) for buffer bind scope

* support batch matmul

* Move cuda env check to tensor_core.cc

* Coderefine for tensor_core.cc

* Refine comments

* Some refinements of code and comment

* Update TensorCore UT to pass the CPU test

* remove redundant code

* matmul's storage align for different layout

* Add support for differenct position of type cast

* Add formal tutorial for auto tensorcore codegen

* move tensorcore check up to tutorial code

* code and doc refine

* comment out tune_and_evaluate in tutorial

* fix cpplint error