ggml-cuda: provide static workspace for cuBLAS handles (#26574)

* provide static workspace for cuBLAS handles

* account for concurrent streams when using GGML_CUDA_GRAPH_OPT

* drop cublas_handle overloads and remove direct cublasSetStream calls

* Update ggml/src/ggml-cuda/common.cuh

---------

Co-authored-by: Oliver Simons <osimons@nvidia.com>

ggml/src/ggml-cuda/out-prod.cu

@@ -54,8 +54,6 @@ void ggml_cuda_out_prod(ggml_backend_cuda_context & ctx, ggml_tensor * dst) {
     const float alpha = 1.0f;
     const float beta = 0.0f;
 
-    CUBLAS_CHECK(cublasSetStream(handle, stream));
-
     const int64_t lda = nb01 / sizeof(float);
     const int64_t ldc = nb1  / sizeof(float);