pageserver: fix AUX key vectored get validation

[VladLazar]

Problem

The value reconstruct of AUX_FILES_KEY from records is not deterministic since it uses a hash map under the hood.
This caused vectored get validation failures when enabled in staging.

Summary of changes

Deserialise AUX_FILES_KEY blobs comparing. All other keys should reconstruct deterministically,
so we simply compare the blobs.

Testing

Tested this locally with data extracted from a tenant which ran into this problem in staging.

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[koivunej]

Looking good after the removal of repeated left and right (repeated after assert_eq! macro has already done that).

[github-actions]

2484 tests run: 2361 passed, 0 failed, 123 skipped (full report)

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Code coverage* (full report)

• functions: 28.8% (6963 of 24204 functions)
• lines: 47.3% (42649 of 90238 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
a9e0d09 at 2024-03-05T13:17:42.607Z :recycle:}