Make graph_max_nodes vary by ubatch size (#17794)
* Make graph_max_nodes vary by ubatch size for models where chunking might explode the graph
* Update src/llama-context.h
Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
* Add missing const
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Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
