tests: stabilize compat tests

[jcsp]

This test had two flaky failure modes:

• pageserver log error for timeline not found: this resulted from changes for DR when timeline destroy/create was added, but endpoint was left running during that operation.
• storage controller log error because the test was running for long enough that a background reconcile happened at almost the exact moment of test teardown, and our test fixtures tear down the pageservers before the controller.

Closes: #7224

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]

2718 tests run: 2581 passed, 0 failed, 137 skipped (full report)

---

Code coverage* (full report)

• functions: 28.1% (6287 of 22345 functions)
• lines: 47.0% (44221 of 94108 lines)

* collected from Rust tests only

---

_{The comment gets automatically updated with the latest test results
8027012 at 2024-03-25T14:17:53.839Z :recycle:}

[bayandin]

Makes sense to me, thanks!