tests: further stabilize test_deletion_queue_recovery

[jcsp]

This is the other main failure mode called out in #6092 , that the test can shut down the pageserver while it has "future layers" in the index, and that this results in unexpected stats after restart.

We can avoid this nondeterminism by shutting down the endpoint, flushing everything from SK to PS, checkpointing, and then waiting for that final LSN to be uploaded. This is more heavyweight than most of our tests require, but useful in the case of tests that expect a particular behavior after restart wrt layer deletions.

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[github-actions]

2754 tests run: 2630 passed, 0 failed, 124 skipped (full report)

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Flaky tests (1)

Postgres 14

• test_ts_of_lsn_api: debug

Code coverage* (full report)

• functions: 28.0% (6405 of 22857 functions)
• lines: 46.9% (45089 of 96237 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
de7a7ec at 2024-04-07T21:34:21.443Z :recycle:}