CANN: add support for ACL Graph (ggml-org#15065)

* feat(cann): add optional support for ACL Graph execution

This commit adds support for executing ggml computational graphs using
Huawei's ACL graph mode via the USE_CANN_GRAPH flag. The support can be
enabled at compile time using the CMake option:

    -DUSE_CANN_GRAPH=ON

By default, ACL graph execution is **disabled**, and the fallback path
uses node-by-node execution.

Key additions:
- CMake option  to toggle graph mode
- Graph capture and execution logic using
- Tensor property matching to determine whether graph update is required
- Safe fallback and logging if the environment variable LLAMA_SET_ROWS
  is unset or invalid

This prepares the backend for performance improvements in repetitive graph
execution scenarios on Ascend devices.

Signed-off-by: noemotiovon <[email protected]>

* Fix review comments

Signed-off-by: noemotiovon <[email protected]>

* remane USE_CANN_GRAPH to USE_ACL_GRAPH

Signed-off-by: noemotiovon <[email protected]>

* fix typo

Signed-off-by: noemotiovon <[email protected]>

---------

Signed-off-by: noemotiovon <[email protected]>

Author: noemotiovon

ggml/src/ggml-cann/common.h

@@ -375,16 +375,6 @@ struct ggml_backend_cann_context {
     cann_task_queue task_queue;
     bool async_mode;
     bool support_set_rows;
-    // Rope Cache
-    void* rope_init_ptr = nullptr;
-    void* rope_sin_ptr = nullptr;
-    void* rope_cos_ptr = nullptr;
-    int64_t max_prompt_length = 0;
-    // Constant Pool
-    void* f32_zero_cache = nullptr;
-    void* f32_one_cache = nullptr;
-    int64_t f32_zero_cache_element = 0;
-    int64_t f32_one_cache_element = 0;
 
     aclrtStream streams[GGML_CANN_MAX_STREAMS] = {nullptr}; /**< Array of streams for the device. */