[Export]: Mem buffer type inferred from graph output type

Context

Change determination of memory ctype when defining the mem memory buffer to use output tensor type instead of the first input tensor type. This allows to test graphs which actually do not have inputs (i.e. all inputs are constant producers).

Modified files

Changed template network_forward.jinja to have a mem_ctype attribute.

Pass the mem_ctype from export() function.

Detailed major modifications

No major modification, just change in the forward function template.

TODO

No TODO forcasted.