Adds support for external parameters in stateless llama along with so…

…me flags

 - Enables use of external parameters for stateless llama example
 - Provides mapping for llama.cpp gguf weights to torch llama weights
 - Adds flag --external_weight_file for path containing weights to load when using run_vmfb
 - Adds flag --vmfb_path for path to vmfb file when using run_vmfb
 - Adds flag --external_weights for generating IR/VMFB with global params expected from external file