[clang][CodeGen] Add AS for Globals to SPIR & SPIRV datalayouts (#88455)

Currently neither the SPIR nor the SPIRV targets specify the AS for
globals in their datalayout strings. This is problematic because
CodeGen/LLVM will default to AS0 in this case, which produces Globals
that end up in the private address space for e.g. OCL, HIPSPV or SYCL.
This patch addresses it by completing the datalayout string.