[nnc][utils][model_generator] Add operation tree. (#2133)

[nnc][utils][model_generator] Add operation tree. (#2133)

The changes add the tree of operations and builder for it.
The tree represents random model without relation
to specific format (TFLite or caffe).

The changes are needed for building random links
between operations with consistency tensor's shapes.
The tree then will be converted to specific format
(in future pull request).

Currently contains only one operation (other in future PR)

Signed-off-by: i-kulagin i.kulagin@samsung.com