[mlir][sparse] cleanup ABI issues in C interface with memrefs

This change adds automatic wrapper functoins with emit_c_interface
to all methods in the sparse support library that deal with MEMREFs.
The wrappers will take care of passing MEMREFs by value internally
and by pointer externally, thereby avoiding ABI issues across platforms.

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D110219