[v1.x] Add onnx export operator unit tests.

[josephevans]

Description

Fixes the following export functions by casting the input and output to the proper data types:

• broadcast_logical_and
• broadcast_logical_or
• broadcast_logical_xor
• logical_not

Adds unit tests for the following ONNX export operators:

• reciprocal
• _power
• broadcast_power
• sqrt
• depth_to_space
• space_to_depth
• square
• shape_array
• hard_sigmoid
• broadcast_lesser
• broadcast_greater
• broadcast_logical_and
• broadcast_logical_or
• broadcast_logical_xor
• logical_not
• log_softmax
• broadcast_to

[mxnet-bot]

Hey @josephevans , Thanks for submitting the PR
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[Zha0q1]

LGTM!