model: Add Mimo v2.5 model support (#22493)

* add mimo-v2.5 support

* mimo-v2.5: fix modify_tensors row split

* mimi-v2.5: forgot `add_attn_value_scale` plumbing

* mimi-v2.5: fix tp dequant to detect tp rows

* mimo-v2.5: fix TP iteration to be descending

* mimo-v2.5: fix comment

* mimo-v2.5: retain fused qkv

* mimo-v2.5: missed the attn_value scale during merge

* mimo-v2.5: fused QKV needs contiguous for scaling attention value

* mimo-v2.5: move `speech_embeddings.` to TextModel filter_tensors

* Update src/llama-hparams.h

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* Update src/models/mimo2.cpp

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* Update src/models/mimo2.cpp

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* Update convert_hf_to_gguf.py

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* Update convert_hf_to_gguf.py

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* Update src/models/mimo2.cpp

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

* mimo-v2.5: include MTP weights in gguf

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Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>