chore(pageserver): warn on delete non-existing file

[skyzh]

Problem

Consider the following sequence of migration:

1. user starts compute
2. force migrate to v2
3. user continues to write data

At the time of (3), the compute node is not aware that the page server does not contain replication states any more, and might continue to ingest neon-file records into the safekeeper. This will leave the pageserver store a partial replication state and cause some errors. For example, the compute could issue a deletion of some aux files in v1, but this file does not exist in v2. Therefore, we should ignore all these errors until everyone is migrated to v2.

Also note that if we see this warning in prod, it is likely because we did not fully suspend users' compute when flipping the v1/v2 flag.

Summary of changes

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]

3150 tests run: 3017 passed, 0 failed, 133 skipped (full report)

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Flaky tests (1)

Postgres 16

• test_vm_bit_clear_on_heap_lock: debug

Code coverage* (full report)

• functions: 31.4% (6492 of 20672 functions)
• lines: 48.4% (50207 of 103759 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
913c1d4 at 2024-05-30T14:54:51.223Z :recycle:}