feat: pre-fill OIDC login role from URL

[evan-cohen]

Description

Pre-fills the OIDC login role from the URL query string.

Closes #31340

TODO only if you're a HashiCorp employee

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PCI review checklist

• I have documented a clear reason for, and description of, the change I am making.
• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.
• If applicable, I've documented the impact of any changes to security controls.

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