llama : model-based max number of graph nodes calculation

[nicoboss]

This fixes #8950 and #8615 This PR builds on top of the changes made in #8622

Calculate the max number of nodes using max(8192, model.tensors_by_name.size()*5) as recommended by @slaren in https://github.com/ggerganov/llama.cpp/issues/8950#issuecomment-2278807100. I specified 8192 as minimum to ensure this change will not break any currently working models.

Thanks to this change I was able to run inference on BigLlama-3.1-681B-Instruct and Meta-Llama-3-405B-Instruct-Up-Merge booth of which did not load prior to this change.

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