pageserver: eliminate CalculateSyntheticSizeError::LsnNotFound (test_metric_collection flake)

[jcsp]

Problem

ERROR synthetic_size_worker: failed to calculate synthetic size for tenant ae449af30216ac56d2c1173f894b1122: Could not find size at 0/218CA70 in timeline d8da32b5e3e0bf18cfdb560f9de29638\n')

e.g. https://neon-github-public-dev.s3.amazonaws.com/reports/main/9518948590/index.html#/testresult/30a6d1e2471d2775

This test had allow lists but was disrupted by #8051. In that PR, I had kept an error path in fill_logical_sizes that covered the case where we couldn't find sizes for some of the segments, but that path could only be hit in the case that some Timeline was shut down concurrently with a synthetic size calculation, so it makes sense to just leave the segment's size None in this case: the subsequent size calculations do not assume it is Some.

Summary of changes

• Remove CalculateSyntheticSizeError::LsnNotFound and just proceed in the case where we used to return it
• Remove defunct allow list entries in test_metric_collection

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]

3216 tests run: 3074 passed, 0 failed, 142 skipped (full report)

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Flaky tests (2)

Postgres 15

• test_pageserver_restarts_under_worload: release

Postgres 14

• test_statvfs_pressure_usage: debug

Code coverage* (full report)

• functions: 31.5% (6633 of 21064 functions)
• lines: 48.6% (51628 of 106300 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
c7f685a at 2024-06-14T19:32:21.435Z :recycle:}