llama: fix llama-model-saver (#20503)

* llama : add fd-based model loading via llama_model_load_from_fd

* llama : address review feedback for fd-based model loading

* llama : use FILE pointer instead of fd in public API

* llama : use FILE pointer consistently, address review feedback

* fixup

* fix tensor names

* fix llama-model-saver

* roundtrip tests

* fixup

* refactor tests

* fix prints

* fix model saving

* fix CI, disable Chameleon

* print seed

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Co-authored-by: Siddhesh2377 <siddheshsonar2377@gmail.com>

src/llama-mmap.h

@@ -15,6 +15,7 @@ using llama_mlocks = std::vector<std::unique_ptr<llama_mlock>>;
 
 struct llama_file {
     llama_file(const char * fname, const char * mode, bool use_direct_io = false);
+    llama_file(FILE * file);
     ~llama_file();
 
     size_t tell() const;