llama : add support for StarCoder model architectures (#3187)

llama : add support for StarCoder model architectures (#3187)

* add placeholder of starcoder in gguf / llama.cpp

* support convert starcoder weights to gguf

* convert MQA to MHA

* fix ffn_down name

* add LLM_ARCH_STARCODER to llama.cpp

* set head_count_kv = 1

* load starcoder weight

* add max_position_embeddings

* set n_positions to max_positioin_embeddings

* properly load all starcoder params

* fix head count kv

* fix comments

* fix vram calculation for starcoder

* store mqa directly

* add input embeddings handling

* add TBD

* working in cpu, metal buggy

* cleanup useless code

* metal : fix out-of-bounds access in soft_max kernels

* llama : make starcoder graph build more consistent with others

* refactor: cleanup comments a bit

* add other starcoder models: 3B, 7B, 15B

* support-mqa-directly

* fix: remove max_position_embeddings, use n_train_ctx

* Update llama.cpp

Co-authored-by: Georgi Gerganov <redacted>
* Update llama.cpp

Co-authored-by: Georgi Gerganov <redacted>
* Apply suggestions from code review

Co-authored-by: Georgi Gerganov <redacted>
* fix: switch to space from tab

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Co-authored-by: Georgi Gerganov <redacted>