tests: perform graceful rolling restarts in storcon scale test

[VladLazar]

Problem

Scale test doesn't exercise drain & fill.

Summary of changes

Make scale test exercise drain & fill

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[bot]]

2998 tests run: 2872 passed, 0 failed, 126 skipped (full report)

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Flaky tests (1)

#### Postgres 16 - `test_isolation[None]`: [debug](https://neon-github-public-dev.s3.amazonaws.com/reports/pr-8173/9682973171/index.html#suites/158be07438eb5188d40b466b6acfaeb3/1883e167e4596675/retries)

Code coverage* (full report)

• functions: 32.8% (6892 of 21018 functions)
• lines: 50.3% (53892 of 107207 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
02e8c57acd6e2b986849f552ca30280d54699b79 at 2024-06-26T17:55:49.845Z :recycle:}