llama : parameter conversion and loading fixes for PLaMo2 variants (#16075)

llama : parameter conversion and loading fixes for PLaMo2 variants (#16075)

* Fix to use hidden_size_per_head

* Fix num heads

* Fix array

* Fix loading weights

* Support old GGUF converted by the previous version of llama.cpp

* Update src/llama-model.cpp

Co-authored-by: Sigbjørn Skjæret <redacted>
* Move shared parameter definitions to the outside of loop

* Not calculating n_embd_head_k,v by n_embd / n_head

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Co-authored-by: Sigbjørn Skjæret <redacted>