Refactor file llama.cpp (#823)

* llama_model and llama_hparams

* llama_build_context

Surprisingly small reduction in llama.cpp compile time given
the reduction in LOCs (22k -> 14k)

* LLM_TN

llama.cpp compilation: 50 s -> 33 s

* llama_quantize

* arch names

* All graph building is now in llm-build-context.cpp

* hparams loading

llama.cpp is now just 9300 LOC, but still takes 32 seconds to compile.

* We are now at 6 seconds to build the src folder

* load -> create

We are not actually loading the tensors, but just creating them.

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Co-authored-by: Iwan Kawrakow <iwan.kawrakow@gmail.com>

src/llama-arch.h

@@ -298,3 +298,5 @@ enum llm_tensor {
 };
 
 llm_arch llm_arch_from_string(const std::string & name);
+
+const char * llama_model_arch_name(llm_arch arch);