Add Qwen2.5 Instruct model

[ITHwang]

Model Support

• candle-examples:
  • added Qwen2, Qwen2.5 Instruct models
  • added quantized Qwen2.5 Instruct models
• candle-wasm-examples:
  • added Qwen2.5 Instruct wasm demo

Etc.

• candle-transformers/src/models/quantized_qwen2.rs:
  • added a factory method from_vb() which creates ModelWeights from VarBuilder.
• candle-transformers/src/quantized_nn.rs:
  • added a factory method from_arc() which creates RmsNorm from Arc<QTensor>.

Related Issues

• Can I add Qwen Instruct models? #2792