model : add support for Seed-OSS (#15490)

model : add support for Seed-OSS (#15490)

* First draft

* Fix linter errors

* Added missing sinks nullptr

* Don't forget the llama-arch!

* We're through to the generation stage.

* Fix post-attention norm

* Apply suggestions from code review

Co-authored-by: Sigbjørn Skjæret <redacted>
* Fix RoPE type

* Fix tensor name and reorder llm_types

* Update gguf-py/gguf/constants.py

Remove nonexistent FFN_POST_NORM tensor

Co-authored-by: Sigbjørn Skjæret <redacted>
* Update src/llama-model.h

Co-authored-by: Sigbjørn Skjæret <redacted>
* Add basic chat template

* Add chat template tests

* Remake chat template test

* Apply suggestions from code review

Co-authored-by: Sigbjørn Skjæret <redacted>
* Update src/llama-chat.cpp

Co-authored-by: Sigbjørn Skjæret <redacted>
* Reorder llm type descriptions

* Update src/llama-model.cpp

Co-authored-by: Sigbjørn Skjæret <redacted>
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Co-authored-by: Sigbjørn Skjæret <redacted>