Option to be less OOP in DPC++

[sravanikonda]

Request to provide access to thread id, group id, memory fence, barrier functions, etc. without using an nd_item like object

[mkinsner]

We're working on exposing some of the queries as free functions. Synchronization (e.g. barrier) will still require a form of grouping object to avoid common programming errors, but we can revisit this.

[mkinsner]

The following extension provides access to IDs without passing them through function call chains. Does this cover enough of the request, and do you have any feedback?

https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/FreeFunctionQueries/SYCL_INTEL_free_function_queries.asciidoc