What type of PR is this?

/kind feature

What does this PR do / why do we need it:
This PR removes the tensor.size() method and add tensor.ndim and tensor.size properties. This PR provides user with more numpy-native experience when using mindspore.

Which issue(s) this PR fixes:

Fixes #I2A0FB:Renaming tensor.size() to tensor.size, and add tensor.ndim

Special notes for your reviewers: