Add Qwen3 0.6B, 1.7B, and 4B (#10539)

Add ExecuTorch support for Qwen3 0.6B, 1.7B, and 4B

### Qwen3 0.6B
Export with xnnpack + 8da4w quantization
```
python -m examples.models.llama.export_llama --model qwen3-0_6b --params examples/models/qwen3/0_6b_config.json -kv --use_sdpa_with_kv_cache -X --xnnpack-extended-ops -d fp32 --output_name="qwen3-0_6b_x_8da4w.pte" --verbose -qmode 8da4w
```

Run with pybindings
```
python -m examples.models.llama.runner.native --model qwen3-0_6b --pte qwen3-0_6b_x_8da4w.pte  --tokenizer ~/.cache/huggingface/hub/models--Qwen--Qwen3-0.6B/snapshots/a9c98e602b9d36d2a2f7ba1eb0f5f31e4e8e5143/tokenizer.json --tokenizer_config ~/.cache/huggingface/hub/models--Qwen--Qwen3-0.6B/snapshots/a9c98e602b9d36d2a2f7ba1eb0f5f31e4e8e5143/tokenizer_config.json --prompt "Who is the president of the US?" --params examples/models/qwen3/0_6b_config.json --max_len 128 -kv --temperature 0.6

>> Okay, let's see. The user is asking about the president of the US, but they wrote "And who is the president of the US?" and "And who is the president of the US?" So maybe they are using the same question but in a different way. They might be referring to the same president. Let me check. ...

# Some rough stats
Prefill time: 0.24 s
Generation tok/s: 17.15 s
Memory: 826.68 MB
```

### Qwen3 1.7B
Export with xnnpack + 8da4w quantization
```
python -m examples.models.llama.export_llama --model qwen3-1_7b --params examples/models/qwen3/1_7b_config.json -kv --use_sdpa_with_kv_cache -X --xnnpack-extended-ops -d fp32 --output_name="qwen3-1_7b_x_8da4w.pte" --verbose -qmode 8da4w
```

Run with pybindings
```
python -m examples.models.llama.runner.native --model qwen3-1_7b --pte qwen3-1_7b_x_8da4w.pte  --tokenizer ~/.cache/huggingface/hub/models--Qwen--Qwen3-0.6B/snapshots/a9c98e602b9d36d2a2f7ba1eb0f5f31e4e8e5143/tokenizer.json --tokenizer_config ~/.cache/huggingface/hub/models--Qwen--Qwen3-0.6B/snapshots/a9c98e602b9d36d2a2f7ba1eb0f5f31e4e8e5143/tokenizer_config.json --prompt "Who is the president of the US?" --params examples/models/qwen3/1_7b_config.json --max_len 128 -kv --temperature 0.6

# Some rough stats
Prefill time: 0.25 s
Generation tok/s: 16.87 s
Memory: 1.02 GB
```

### Qwen3 4B
Export with xnnpack + 8da4w quantization
```
python -m examples.models.llama.export_llama --model qwen3-4b --params examples/models/qwen3/4b_config.json -kv --use_sdpa_with_kv_cache -X --xnnpack-extended-ops -d fp32 --output_name="qwen3-4b_x_8da4w.pte" --verbose -qmode 8da4w
```

Run with pybindings
```
python -m examples.models.llama.runner.native --model qwen3-4b --pte qwen3-4b_x_8da4w.pte  --tokenizer ~/.cache/huggingface/hub/models--Qwen--Qwen3-0.6B/snapshots/a9c98e602b9d36d2a2f7ba1eb0f5f31e4e8e5143/tokenizer.json --tokenizer_config ~/.cache/huggingface/hub/models--Qwen--Qwen3-0.6B/snapshots/a9c98e602b9d36d2a2f7ba1eb0f5f31e4e8e5143/tokenizer_config.json --prompt "Who is the president of the US?" --params examples/models/qwen3/4b_config.json --max_len 128 -kv --temperature 0.6

# Some rough stats
Prefill time: 0.44 s
Generation tok/s: 12.12 s
Memory: 2.5 GB
```

bypass-github-export-checks