Support QAT in QCOM qnn backend

[cccclai]

🚀 The feature, motivation and pitch

Currently qnn quantizer only supports PTQ (post training quantization), and we'd like to enable QAT (quantization aware trainning) for better quantization support

Alternatives

Use PTQ

Additional context

No response

RFC (Optional)

No response

[cccclai]

Hi @chiwwang, @navsud is our quantization expert and is also looking into QAT for qnn, maybe we can coordinate and enable QAT together.

[chiwwang]

Nice! ++ @chunit-quic , who is prototyping QAT in qnn quantizer.

[chiwwang]

We have a prototype #6222, which is more like kickoff for our discussions.
It might be incorrect.... QAT is really a new thing for us. So please feel free to advise and give directions! (And...what model is suitable for the 1st QAT target? We need some E2E verifications... 🤔 )

[cccclai]

PR is merged. Feature is ready