add new function ptq first then initialize qat scale with ptq scale

[ZhangHandi]

PR types

New features

PR changes

APIs

Describe

instead of save ptq model, then load it before qat, now we can initialize qat scale directly with ptq scale. Two variable are added in config, 'quant_post_first' decides whether ptq first, 'scale_trainable' decides whether to train scale during qat.

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