CUDA: Add mul_mat_id support for the mmf kernel (#15767)

* CUDA: Add mul_mat_id support the mmf

Add support for mul_mat_id for bs < 16

* Review: use warp_size, fix should_use_mmf condition

* Launch one block per expert, stride along n_expert_used

* templatize mul_mat_id

* Pad shmem to 16 bytes, add helper function mul_mat_f_switch_ids

* Reduce compile times by dividing mmf into f16, bf16 and f32 variants

* Divide mmf by ncols_dst

* Add missing files

* Fix MUSA/HIP builds

ggml/src/ggml-cuda/template-instances/mmf-instance-ncols_3.cu

@@ -0,0 +1,5 @@
+// This file has been autogenerated by generate_cu_files.py, do not edit manually.
+
+#include "../mmf.cuh"
+
+DECL_MMF_CASE(3);