Created by: wojtuss

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• PR type（PR 类型） is (C, F ): A. New features（新功能）---------------- D. Performance optimization（性能优化） B. Bug fixes（问题修复）------------------ E. Breaking changes（向后不兼容的改变） C. Function optimization（功能优化）------F. Others（其它）

• PR changes（改动点）is (C, D ): A. OPs（operators）---------------------- C. Docs（文档） B. APIs（接口）--------------------------- D. Others（其它）

• Use one sentence to describe what this PR does.（简述本次PR的目的和改动） Improves QAT INT8 quantization process.

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• Describe what this PR does in detail. If this PR fixes an issue, please give the issue id.

With this patch, the following updates are made to QAT:

• added the --op_ids_to_skip option to exclude operators from quantization by their id numbers,
• added the --debug option to enable the generation of graphviz *.dot files after each step of the graph transformation,
• improved quantization of operators with missing output quantization scale,
• improved logging during quantization,
• enabled optimization of the FP32 model,
• fixed quantizing unsigned output data after relu op or postop,
• updated the QAT documentation.

With the help of the --op_ids_to_skip and --debug options the accuracy of the pvnet_ocr model after quantization was improved greatly. See the issue https://github.com/PaddlePaddle/Paddle/issues/24461 for details.

• If you modified docs, please make sure that both Chinese and English docs were modified and provide a preview screenshot. （文档必填）

• Please write down other information you want to tell reviewers.