Remove padding and multiple D2D copies for MTP (#24086)

* Make ggml_gated_delta_net take only the initial recurrent state (D, 1, n_seqs) and passes the snapshot count K as an op parameter instead of inferring it from state->ne[1].

Remove the padding hack and copy all emitted snapshots into the recurrent cache with a single strided ggml_cpy

* Make GDN changes in all backends. Address review comments.

* Fix CI build errors

ggml/src/ggml-cpu/ggml-cpu.c

@@ -2948,7 +2948,7 @@ struct ggml_cplan ggml_graph_plan(
                 case GGML_OP_GATED_DELTA_NET:
                     {
                         const int64_t S_v = node->src[2]->ne[0];
-                        const int64_t K   = node->src[5]->ne[1];  // state is (D, K, n_seqs)
+                        const int64_t K   = ggml_get_op_params_i32(node, 0);
                         const int64_t per_thread = S_v + (K > 1 ? S_v * S_v : 0);
                         cur = per_thread * sizeof(float) * n_tasks;
                     } break;