ggml : recurrent state rollback for ggml_ssm_scan (llama/26623)

* Initial changes for Recurrent state rollback for nemotron for cpu and cuda

* Removing CPU RS rollback. Will enable it in subsequent PRs

* addition of test case

* Removing assert and calling runtime API to check if op is supported

* removing extra API and updating the call sites for K

* replace static cuda detection to runtime fused_op api

* address review comments and fallback when SSM rollback not supprted

* Adding changes for supporting RS-rollback in CPU. Also added test-backend-ops for cpu and cuda

* removing memory manipulation as rs rollback is now supported in CPU

* removing the static probe which is not needed now

* correcting the format

* address review comments

* enabling test for all the backends, unsupported backends will fallback to CPU

* Apply suggestions from code review

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* choose different graph based on the result of fused_ssm_op is supported or not and also handled memory->n_rs_seq >1 case incase of op is not supported

* Support K > 1 in ssm_scan for all backends

* Fix CI Issues

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Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
Co-authored-by: Gaurav Garg <gaugarg@nvidia.com>

ggml/src/ggml-cpu/ggml-cpu.cpp

@@ -472,6 +472,8 @@ static bool ggml_backend_cpu_device_supports_op(ggml_backend_dev_t dev, const st
                 src1->type == GGML_TYPE_F32 && op->type == GGML_TYPE_F32;
         case GGML_OP_CONV_2D:
             return ggml_is_contiguous(op->src[0]);
+        case GGML_OP_SSM_SCAN:
+            return ggml_get_op_params_i32(op, 0) == 1 || op->src[3]->ne[0] == 1;
         default:
             return true;
     }