Testing all BF16/FP16 combinations for TPPs

[alheinecke]

#794 has shown we have some holes in the testing infra, that we should fix by running all tests with not only pure f16 and b16 inputs, but also their combinations.

[hfp]

I second this issue even if #794 is currently classified as a compiler bug, i.e., caused by glue code rather than our kernels. The cause seems to be still unclear to me as there is no clear reproducer yet.