Port micro op GATHER_ND and its test code from lite

[rsun-bdti]

Issue #46268. This PR aims to finish porting GATHER_ND from TFL to TFLM.
(This PR combines the originally planned PRS 3, 4, and 5)

Notes:
1 For params/output tensors, only the float and int8_t data types are supported;
2 For indices tensors, only the int32_t data type is supported;
3 The reference implementation in lite/kernels/internal/reference/reference_ops.h was not used, due to the vector used in the reference (possible dynamic allocation);
4 As with the TFL kernel Gather_ND, the TFLM kernel does not yet support batch_dims as of April 23, 2021.

[google-ml-butler]

Thanks for contributing to TensorFlow Lite Micro.

To keep this process moving along, we'd like to make sure that you have completed the items on this list:

• Read the contributing guidelines for TensorFlow Lite Micro
• Created a TF Lite Micro Github issue
• Linked to the issue from the PR description

We would like to have a discussion on the Github issue first to determine the best path forward, and then proceed to the PR review.

[google-cla]

☹️ Sorry, but only Googlers may change the label cla: yes.