[mlir] Add alloca address space handling to the data layout subsystem

[mlir] Add alloca address space handling to the data layout subsystem

This patch adds alloca address space information to the data layout interface
and implementation in the DLTI dialect. This is needed for targets that use
separate address spaces for local/stack data.

Reviewed By: ftynse, krzysz00

Differential Revision: https://reviews.llvm.org/D144657