shared memory update

[pkicsiny]

• updated context_cupy.py so that the shared memory size is now inferred from the kernel description argument. If such an argument is not given in the kernel description, then the default value (=0) is used.

[giadarol]

Could you remind me why is the shared memory size a property of the context and not of the kernel?

[pkicsiny]

I made it such that it can be used for any other kernels, same ways as the default_block_size property.