[backend_cpu] Error in WeightInterLEaving tests because of DataFormat

Context

There is an ambiguity toward the management of DataFormat::Default value.

In some cases it is handled as implicitly being equal to DataFormat::NCHW (in getDataFormatTranspose) and sometimes it is implicitly "unspecified" and ready to be replaced by any format without any modifications in the Tensor.

By changing the behaviour in the setDataFormat and removing the Default format (which was previously considered undefined and ready to be replaced by any format without any modifications), the Default format was now treated as NCHW.

Solution

The original behaviour of unspecified DataFormat::Default should be implemented back and its behaviour made more resilient.