[MXNET-1330] Bring nnvm::Tuple to mxnet::Tuple

[junrushao]

Description

This PR is the initial part of efforts for the numpy module of MXNet #14253, in which we bring nnvm's Tuple and TShape into MXNet for all further changes to happen locally in MXNet. See the section "Changes" for details.

Test coverage is ensured automatically ensured by our CI pipeline, because this PR is checked by all testcases related to any NDArray's shape.

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [MXNET-$JIRA_ID], where $JIRA_ID refers to the relevant JIRA issue created (except PRs with tiny changes)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage:
• Unit tests are added for small changes to verify correctness (e.g. adding a new operator)
• Nightly tests are added for complicated/long-running ones (e.g. changing distributed kvstore)
• Build tests will be added for build configuration changes (e.g. adding a new build option with NCCL)
• Code is well-documented:
• For user-facing API changes, API doc string has been updated.
• For new C++ functions in header files, their functionalities and arguments are documented.
• For new examples, README.md is added to explain the what the example does, the source of the dataset, expected performance on test set and reference to the original paper if applicable
• Check the API doc at http://mxnet-ci-doc.s3-accelerate.dualstack.amazonaws.com/PR-$PR_ID/$BUILD_ID/index.html
• To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

Changes

• Bring nnvm::Tuple to mxnet::Tuple
• Bring nnvm's passes into MXNet, including MXGradient, MXPlanMemory
• Refactor the code a little bit by explicitly requiring "mxnet::" prefix, and using the alias "mxnet::ShapeVector" instead of "std::vector".

Comments

• Thanks @reminisce for great suggestions.

[reminisce]

Thanks for being willing to making so many micro-surgical changes scattered all over the places.

[junrushao]

Hi, the CI has passed. Could someone kindly review and merge this PR if you have time? @szha @zheng-da @reminisce @eric-haibin-lin