chore: support hadron JWT set-up

[VladLazar]

This is a hadron port to support the Hadron flavour of JWT tokens (original PR is #179).
I recommend the reviewer reads the original cover letter.

On top of that I changed:

• endpoint_storage now uses the common JWT utilities which know how to differentiate between neon and hadron jwt
• a lot of wrangling in control_plane
• parametrise auth tests to use both neon and hadron JWT

[github-actions]

9174 tests run: 8520 passed, 0 failed, 654 skipped (full report)

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Flaky tests (1)

Postgres 17

• test_pageserver_restart: release-arm64-without-lfc

Code coverage* (full report)

• functions: 34.7% (8847 of 25493 functions)
• lines: 45.7% (71730 of 156847 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
a1cc1f3 at 2025-07-31T11:39:13.507Z :recycle:}

[erikgrinaker]

LGTM, ignoring style/design issues to avoid code churn. Just skimmed test changes.

[MMeent]

(original PR is #179).

I have some serious doubts about that.

[erikgrinaker]

(original PR is #179).

I have some serious doubts about that.

In the internal Hadron repo.

[williamhuan-db]

Eyeballed through all the changes, should be fine. Just some comments on the potential new conflicts this may create and see if we can reduce some.