[SYCL] Trim properties header dependencies (#21709)
Reduce transitive include cost in the ext::oneapi properties headers by
removing the dependency on sycl/detail/type_traits.hpp for nth_type_t,
switching iosfwd to cstddef, and dropping an unused include. Keep the
detail namespace behavior compatible with existing users.
This change reduces the transitive included headers from 41 to 28 for
both host and device compilation saving roughly 20ms of compile time.
