[SYCLomatic] device pointer wrapper APIs

[danhoeflinger]

Draft PR: Extra APIs in NO-USM mode to launch algorithm on the device if the incoming input iterator is a pointer. If the input pointers are pointers in the virtual memory space describing a device_pointer, it launches with a device policy, otherwise it launches on the host.

Adds helper function(s) to enable this pattern with minimal code duplication between APIs.

APIs for the following: unique unique_copy merge set_intersection set_symmetric_difference set_difference set_union stable_partition_copy partition_copy equal_range