[mlir][DRR] Add location directive

Summary:
Add directive to indicate the location to give to op being created. This
directive is optional and if unused the location will still be the fused
location of all source operations.

Currently this directive only works with other op locations, reusing an
existing op location or a fusion of op locations. But doesn't yet support
supplying metadata for the FusedLoc.

Based off initial revision by antiagainst@ and effectively mirrors GlobalIsel
debug_locations directive.

Differential Revision: https://reviews.llvm.org/D77649