Fix epilogue::thread::Convert cannot be used with DefaultEpilogue

[solrex]

Add the interface types and functions to template class epilogue::thread::Convert which is required by DefaultEpilogue.

Testing code:

  using CollectiveEpilogue = cutlass::epilogue::collective::DefaultEpilogue<
      ElementD,
      cutlass::detail::TagToStrideC_t<LayoutC>,
      cutlass::detail::TagToStrideC_t<LayoutD>,
      cutlass::epilogue::thread::Convert<ElementD, AlignmentD, ElementAccumulator>,
      cutlass::gemm::EpilogueDefault>;