Run gc on too many partial backup segments

[petuhovskiy]

The general partial backup idea is that each safekeeper keeps only one partial segment in remote storage at a time. Sometimes this is not true, for example if we uploaded object to S3 but got an error when tried to remove the previous upload. In this case we still keep a list of all potentially uploaded objects in safekeeper state.

This commit prints a warning to logs if there is too many objects in safekeeper state. This is not expected and we should try to fix this state, we can do this by running gc.

I haven't seen this being an issue anywhere, but printing a warning is something that I wanted to do and forgot in initial PR.

[github-actions]

3024 tests run: 2891 passed, 0 failed, 133 skipped (full report)

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Flaky tests (5)

Postgres 15

• test_partial_evict_tenant[relative_equal]: release
• test_synthetic_size_while_deleting: release

Postgres 14

• test_compute_pageserver_connection_stress: release
• test_gc_aggressive: release, debug

Code coverage* (full report)

• functions: 31.4% (6324 of 20137 functions)
• lines: 47.3% (47667 of 100781 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
1a97da1 at 2024-05-10T14:19:06.690Z :recycle:}

[arssher]

I wonder if smth specific caused this PR.

[petuhovskiy]

I wonder if smth specific caused this PR.

Not really. Just was thinking about S3 objects count and realized that if we have upload-error-retry loop we can have too many objects and it's hard to spot this.