Add bitnet-embeddings-0.6b model adaptation and GGUF conversion tools

[isHuangXin]

• Add GGUF conversion tool for bitnet-embeddings-0.6b (safetensors -> F16 GGUF and I2_S GGUF)
• Add Qwen3 architecture support in llama.cpp submodule with per-projection RMSNorm
• Add I2_S ternary quantization (2-bit packed -1/0/+1) for lossless precision
• Add f16 norm weight support for correct embedding inference
• Add benchmark and accuracy verification scripts
• Add GGUF layer inspection utilities for F16 and I2_S formats
• Add bitnet-lut-kernels.h placeholder for standalone compilation
• Update llama.cpp submodule to dev-bitnet-embedding-0.6b branch

[isHuangXin]

@microsoft-github-policy-service agree