vulkan/cuda: fix topk_moe with exp_probs_b (#18071)

I updated test_topk_moe to more closely match llm_graph_context::build_moe_ffn
and added coverage for exp_probs_b and some other missing combinations. This
exposed a bug in both CUDA and Vulkan backends where they were assuming the
input to argsort and the input to get_rows are the same. I'd like to optimize
this graph in another change, but for now just get it functional.

CUDA also had a bug where it got n_experts from the wrong place, leading to
GGML_ASSERT failures in some of the new tests.

ggml/src/ggml-cuda/topk-moe.cuh

@@ -11,6 +11,11 @@ void ggml_cuda_op_topk_moe(ggml_backend_cuda_context & ctx,
                            const bool                  delayed_softmax = false,
                            ggml_tensor *               weight_clamp    = nullptr);
 
-bool ggml_cuda_should_use_topk_moe(const ggml_tensor * softmax, const ggml_tensor * weights, const ggml_tensor * clamp = nullptr);
+bool ggml_cuda_should_use_topk_moe(const ggml_tensor * softmax,
+                                   const ggml_tensor * weights,
+                                   const ggml_tensor * get_rows,
+                                   const ggml_tensor * argsort,
+                                   const ggml_tensor * clamp,
+                                   int n_expert);
 
 std::initializer_list<enum ggml_op> ggml_cuda_topk_moe_ops(bool with_norm, bool delayed_softmax = false);