Check URL in validate_api_difference_format based on API URL Parser

[LittleHeroZZZX]

本 PR 将 #7701 中的 API URL Parser 工具引入 validate_api_difference_format.py，并据此对所有 API 差异文档进行格式化，具体包括：

• 在 CI 中增加对差异文档中的 API 链接的检查，若与 Parser 解析出的链接不一致，报错并拦截
• validate_api_difference_format.py 增加 --fix-url参数，支持对错误的 URL 自动修复

[paddle-bot]

感谢你贡献飞桨文档，文档预览构建中，Docs-New 跑完后即可预览，预览链接：http://preview-pr-7723.paddle-docs-preview.paddlepaddle.org.cn/documentation/docs/zh/api/index_cn.html
预览工具的更多说明，请参考：飞桨文档预览工具

[Copilot]

Pull request overview

This pull request standardizes external documentation URLs across PyTorch and PaddlePaddle API mapping documentation files. The changes update URL formats to include complete anchor fragments and switch PyTorch URLs from pytorch.org to the canonical docs.pytorch.org domain.

Changes:

• Updated PyTorch documentation URLs from pytorch.org to docs.pytorch.org domain
• Added complete anchor fragments to URLs (e.g., #torch.adjoint instead of just #torch-adjoint)
• Standardized PaddlePaddle URLs to include complete anchor fragments
• Added underscores to link text where function names contain underscores (e.g., torch.optim.lr_scheduler.ConstantLR → torch.optim.lr\_scheduler.ConstantLR)

[zhwesky2010]

LGTM