Example of FP32 -> BF16 conversion in epilogue of GEMM

[sanchitintel]

Counterpart of examples/00_bmg_gemm/00_bmg_gemm.cpp with BF16 output instead of FP32.
A is BF16, B is BF16, C is FP32, and D is BF16.

Barring a few lines (some of which have been adapted/copy-pasted from https://github.com/intel/cutlass-sycl/blob/e83f147263dd8ca3589b34d76ce6fbec58bac048/test/unit/gemm/device/default_gemm_group_configuration.hpp), the code is almost as same as examples/00_bmg_gemm/00_bmg_gemm.cpp, so ideally, both files' code should be combined. Please use a diff tool such as BeyondCompare to see the difference in both files.

This code isn't adding any new functionality, but is merely an example.

• Add this example to the existing example file

Thanks!