remote_storage: add head_object integration test

[erikgrinaker]

Problem

There was no integration test for head_object. See also #9236 (comment).

Summary of changes

Add a head_object integration test.

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

[github-actions]

5058 tests run: 4872 passed, 0 failed, 186 skipped (full report)

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Flaky tests (2)

Postgres 17

• test_scrubber_physical_gc_ancestors_split: debug-x86-64
• test_subscriber_restart: release-x86-64

Code coverage* (full report)

• functions: 31.4% (7506 of 23903 functions)
• lines: 49.6% (60276 of 121436 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
15f1688 at 2024-10-04T11:57:34.309Z :recycle:}