cuda : CUDA Graph Compute Function Refactor (precursor for performance improvements) (ggml-org#11042)

* Refactor: Moves cuda graph executable update step to separate function.

* Refactor: Moves cuda graph update check to separate function.

* Refactor: Moves cuda graph maintenance (update or adjusting copy parameters) to separate function for improved readability.

* Fix: Adds missing reference to maintain_cuda_graph() definition.

* Refactor: Improves structure and abstractions by moving CUDA graph evaluation and capture to its own function.

* Refactor: Moves node graph checks and copy ops into individual function for improved readability.

* Refactor: Removes code permanently excluded from compilation to increase readability.

* Style: Adds missing newline

* Style: Consolidates several neighboring '#ifdef USE_CUDA_GRAPH' into a single one

* Refactor: Makes 'cuda_graph_update_required' a local variable

* remove double lines between functions

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Co-authored-by: slaren <[email protected]>

Author: 2 people