[SYCL] Add aspect enum value information to LLVM IR metadata

[steffenlarsen]

This commit adds a new module-level metadata node !intel_sycl_aspects which contains metadata pairs of the enum element names and integral values of the SYCL aspects enum, identified by the [[sycl_detail::sycl_type(aspect)]] attribute. This commit also makes the SYCLPropagateAspectsUsage pass read !intel_sycl_aspects and use this information to determine the value of the fp64 aspect instead of relying on it being synchronized with the SYCL implementation headers.