[mlir][gpu] Add the `gpu-module-to-binary` pass.

**For an explanation of these patches see D154153.**

Commit message:
This pass converts GPU modules into GPU binaries, serializing all targets present
in a GPU module by invoking the `serializeToObject` target attribute method.

Depends on D154147

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D154149