[mlir][spirv] Add support for lowering scf.for scf/if with return value

This allow lowering to support scf.for and scf.if with results. As right now
spv region operations don't have return value the results are demoted to
Function memory. We create one allocation per result right before the region
and store the yield values in it. Then we can load back the value from
allocation to be able to use the results.

Differential Revision: https://reviews.llvm.org/D82246