tests: make location_conf_churn more robust

[jcsp]

Problem

This test directly manages locations on pageservers and configuration of an endpoint. However, it did not switch off the parts of the storage controller that attempt to do the same: occasionally, the test would fail in a strange way such as a compute failing to accept a reconfiguration request.

Summary of changes

• Wire up the storage controller's compute notification hook to a no-op handler
• Configure the tenant's scheduling policy to Stop.

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]

3018 tests run: 2903 passed, 0 failed, 115 skipped (full report)

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Flaky tests (3)

Postgres 15

• test_subscriber_restart: release

Postgres 14

• test_statvfs_pressure_usage: debug
• test_replica_query_race: release

Code coverage* (full report)

• functions: 32.6% (6929 of 21268 functions)
• lines: 50.0% (54450 of 108884 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
4b18fc6 at 2024-07-04T19:50:32.750Z :recycle:}