* [RELAY][PASS] FoldScaleAxis Forward

* Introduce helper function type_as

* Update per review comment

* Fix according to comments

GCC issues warnings with -Wextra if we don't explicitly initialize
base class in copy constructors. This commit fixed the issue.

It might cause TupleTypeNode to be printed incorrectly.
it doesnt show in http://ci.tvm.ai:8080/blue/organizations/jenkins/tvm/detail/PR-1989/1/pipeline/141, but if you run it on local machine you will see what get compared being NodeBase and TupleType.

Also as a side thought can we write a giant macro that make sure everything get did right (all field get visited, typekey match, declare_node_type_info match, etc?) I can do some macro metaprogramming, so I can take up the work.

[DOCS] Fix C++ example:graph_runtime.cc:151: Check failed: data->ndim == data_out->ndim (2 vs. 1) (#1987)

* l2 normalization

* retrigger CI

* [RELAY] BiasAdd, MLP, Resnet testing

* fix review comments