fix(pageserver): add dry-run to force compact API

[skyzh]

Problem

Looking at the logs after I ran compaction on some tenants, I realized that dry-run was never part of the API...

Summary of changes

Add dry-run flag to the compact API

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]

3780 tests run: 3674 passed, 0 failed, 106 skipped (full report)

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Flaky tests (1)

Postgres 14

• test_subscriber_restart: release-x86-64

Code coverage* (full report)

• functions: 32.5% (7401 of 22748 functions)
• lines: 50.7% (60060 of 118380 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
8d2e953 at 2024-08-28T20:46:22.985Z :recycle:}