Rename elementwise operation (single source)

[rocking5566]

Rename type, variable and file like
AElementwiseOperation a_element_op
BElementwiseOperation b_element_op
CElementwiseOperation c_element_op
SrcElementwiseOperation src_element_op_
DstElementwiseOperation dst_element_op_
element_wise_reduce_operation
element_wise_operation.hpp

Because we need to add other elementwise operation (two source), to prevent confuse.
We need to rename the original concept. ex: tensor functor

[rocking5566]

We dont have plan to refactor it for now