Pydantic v2

[V02460]

Update Pydantic to v2.

Steps I took to create this change:

1. Remove import indirection
2. Run the Pydantic migration tool
3. Fix remaining issues
4. Enable strict mode and remove check_pydantic_models.py

Notable changes are

1. differing return type for threepid requests with an invalid email
2. changed logic for _metadata_url and _introspection_endpoint
3. changed definition of AnyEventId
4. Disabled strict mode for tuple and set types

Closes #15858
Closes #15979

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
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• Code style is correct (run the linters)