CANN: Refactor `evaluate_and_capture_cann_graph` (llama/17333)

CANN: Refactor `evaluate_and_capture_cann_graph` (llama/17333)

* CANN: Refactor `evaluate_and_capture_cann_graph`

**Description of the problem**

* `matched_graph` is obtained even if graph mode is disabled.
* End of graph capture and graph replay are unnecessarily placed in different `if` blocks.

**Proposed solution**

* Obtain `matched_graph` only if graph mode is enabled.
* Place end of graph capture and graph reply inside the same `if` block.
* Unify graph related comments.

* Remove trailing whitespace