tests: allow-list neon_local endpoint errors from storage controller

[jcsp]

Problem

For testing, the storage controller has a built-in hack that loads neon_local endpoint config from disk, and uses it to reconfigure endpoints when the attached pageserver changes.

Some tests that stop an endpoint while the storage controller is running could occasionally fail on log errors from the controller trying to use its special test-mode calls into neon local Endpoint.

Example: https://neon-github-public-dev.s3.amazonaws.com/reports/pr-8117/9592392425/index.html#/testresult/9d2bb8623d0d53f8

Summary of changes

• Give NotifyError an explicit NeonLocal variant, to avoid munging these into generic 500s (I don't want to ignore 500s in general)
• Allow-list errors related to the local notification hook.

The expectation is that tests using endpoints/workloads should be independently checking that those endpoints work: if neon_local generates an error inside the storage controller, that's ignorable.

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]

2910 tests run: 2793 passed, 0 failed, 117 skipped (full report)

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Code coverage* (full report)

• functions: 32.4% (6850 of 21130 functions)
• lines: 49.9% (53395 of 107068 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
ae9d58d at 2024-06-21T17:02:56.144Z :recycle:}