Count model parameters and size using only the GGUF tensors

[slaren]

Discussed in #10274

The number of parameters and size of the model currently is calculated from the tensors created after the model is loaded, which in some cases may contain duplicated tensors, resulting in an inaccurate and inconsistent reporting of the model size. To address this, llama_model_n_params and llama_model_size should be modified to return the value as calculated in llama_model_loader::n_elements and n_bytes, which could be stored in llama_model while loading the model.

[FirstTimeEZ]

This issue is fixed by #10286