PartnerAppAuthProvider class support missing in 3.x (similar to 2.x)

**Describe the feature you'd like**
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PartnerAppAuthProvider is the entity used by Sagemaker Partner AI Apps to use for their apps functionality using sagemaker python sdk.

**How would this feature be used? Please describe.**
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Please see https://github.com/aws/sagemaker-python-sdk/blob/master-v2/src/sagemaker/partner_app/auth_provider.py

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**Additional context**
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首先阅读所引用的 master-v2/src/sagemaker/partner_app/auth_provider.py 实现，并将其与 3.x 的包结构进行比较。找出 3.x 中用于 partner app authentication 的对应位置和测试，然后验证 PartnerAppAuthProvider 已公开，并支持文档中说明的 SageMaker Partner AI Apps 用例。

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