`doxygen`: generate a tag file similar to how other `Trilinos` packages do

[romintomasetti]

I seems that kokkos-kernels does not produce a Doxygen tag file for now. This means other packages cannot nicely reference kokkos-kernels functionalities: https://github.com/kokkos/kokkos-kernels/blob/38132f350a7a76dd9436873de303f18255bf6894/docs/Doxyfile.in#L2287

To enable a kokkos-kernels tag file to be available at https://docs.trilinos.org/dev/packages/common/tag_files, I would propose that docs/Doxyfile.in is simply updated to:

 GENERATE_TAGFILE       = ../../common/tag_files/kokkos-kernels.tag

@cwpearson What do you think ? Thanks!