Add passthrough_authorization_parameters support to OIDC configuration (#18232)

# Add passthrough_authorization_parameters support to OIDC configuration

This PR adds `the passthrough_authorization_parameters` option to OIDC
configuration, allowing specific query parameters (like `login_hint`) to
be passed from the redirect endpoint to the authorization grant URL.

This enables clients to provide additional context to identity providers
during authentication flows.

# Pull Request Checklist

<!-- Please read
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* [x] Pull request is based on the develop branch
* [x] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
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@github_username." or "Contributed by [Your Name]." to the end of the
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* [x] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct
(run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))

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Co-authored-by: Quentin Gliech <quenting@element.io>

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