Miscellaneous fix for several numpy issues

[haojin2]

Description

#16658 #16650 and inconsistent type when an array is created from an official numpy array:

from mxnet import np
import numpy as _np
a = np.array(_np.ones((3, ), dtype=_np.float16))
# a's dtype should be float16
# while the previous implementation it was float32
# after this fix it should become float16

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [MXNET-$JIRA_ID], where $JIRA_ID refers to the relevant JIRA issue created (except PRs with tiny changes)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage:
• Unit tests are added for small changes to verify correctness (e.g. adding a new operator)
• Nightly tests are added for complicated/long-running ones (e.g. changing distributed kvstore)
• Build tests will be added for build configuration changes (e.g. adding a new build option with NCCL)
• Code is well-documented:
• For user-facing API changes, API doc string has been updated.
• For new C++ functions in header files, their functionalities and arguments are documented.
• For new examples, README.md is added to explain the what the example does, the source of the dataset, expected performance on test set and reference to the original paper if applicable
• Check the API doc at https://mxnet-ci-doc.s3-accelerate.dualstack.amazonaws.com/PR-$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

• Fix for expand_dims's boolean support
• Fix for [Numpy] Boolean array bug #16658
• Make resulting ndarray's dtype consistent with a source official numpy ndarray
• corresponding tests

Comments

[haojin2]

@eric-haibin-lin Good for merge?