projects/composablekernel: add SwigluStep support for MoE
blockscale (#6118)
## Summary
- add `swiglustep_and_mul` to the composablekernel MoE blockscale
activation enum
- implement the corresponding blockscale epilogue path for `SwigluStep`
- keep existing `silu` and `gelu` paths unchanged
## Scope
This PR covers the classic composablekernel blockscale MoE path under
`projects/composablekernel`.
This is separate from the `ck_tile` / FlatMM path being discussed in
ROCm/rocm-libraries#5992.
## Motivation
`Step-3.5-Flash-FP8` uses `SwigluStep` in its MoE MLP path. The
dependent AITER change needs native support for this activation in the
classic composablekernel MoE blockscale path.
## Validation
- patch is limited to two composablekernel files under
`projects/composablekernel`
- existing `silu` / `gelu` paths are unchanged
- dependent AITER runtime validation hit the classic CK 2-stage path
with AITER MoE enabled
b75afb4274