[SYCL] Add support for templated call operator in functors

[srividya-sundaram]

This PR enables kernels to be defined as named function object types, where the operator() member function is templated.

Example:

class FunctorWithCallOpTemplated {
  int x;
  public:
  template <int x = 0>
  void operator()() const {}
};

q.submit([&](sycl::handler &cgh) {
    cgh.single_task(FunctorWithCallOpTemplated{});
  });

[premanandrao]

LGTM

[srividya-sundaram]

@intel/llvm-gatekeepers Hi, this is ready for merge. Thank you.

[srividya-sundaram]

Hi @tfzhu @yinyangsx
The SYCL / Linux / Build + LIT job has been waiting forever to be picked up from the queue. I haven't seen them take this long.
Can you please take a look? Thank you!

[tfzhu]

Hi @tfzhu @yinyangsx The SYCL / Linux / Build + LIT job has been waiting forever to be picked up from the queue. I haven't seen them take this long. Can you please take a look? Thank you!

2 Linux runners are offline. Fixed and task should be started later

[srividya-sundaram]

@tfzhu I can't tell what's wrong with SYCL / Linux / [AWS] CUDA LLVM Test Suite (pull_request_target) by looking at the log.
Can you please comment if you are aware of what's going on?