[SYCL] Fix bitselect builtin for integer types (#12598)
This regressed after #11956 as return type wasn't correctly converted
from SPIR-V intrinsic back to SYCL types. This PR fixes that.
In addition, I'm also adding tests for `sycl::select` builtin that was
left unaffected only because we couldn't use SPIR-V intrinsic for its
implementation.
