Improved support for OpenCL

Converting all sycl buffers to uninitialised device only buffers; adding memcpyHostToDevice and memcpyDeviceToHost on syclDevice; modifying all examples to obey the new rules; moving sycl queue creating to the device based on Benoit suggestion; removing the sycl specefic condition for returning m_result in TensorReduction.h according to Benoit suggestion.

Generalize IterativeSolverBase::solve to hanlde any sparse type as the results (instead of SparseMatrix only)

Needed for evaluator<Solve>.

Removed the sycl include from Eigen/Core and moved it to Unsupported/Eigen/CXX11/Tensor; added TensorReduction for sycl (full reduction and partial reduction); added TensorReduction test case for sycl (full reduction and partial reduction); fixed the tile size on TensorSyclRun.h based on the device max work group size;

Bug 1330: Cholmod supports double precision only, so let's trigger a static assertion if the scalar type does not match this requirement.

Disable vectorization on device only when compiling for sycl

Fixed the ambiguity in callig make_tuple for sycl backend.

Fix type in lgamma_impl<double>.