Add retry loops and bump test timeout in test_pageserver_connection_stress

[save-buffer]

Problem

Test is still flaky due to two issues: test sometimes times out after 300 sec, and sometimes it fails because a query gets canceled due to it timing out.

Summary of changes

Bumps test timeout and retries queries if they get canceled.

[github-actions]

2856 tests run: 2735 passed, 0 failed, 121 skipped (full report)

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Flaky tests (2)

Postgres 16

• test_vm_bit_clear_on_heap_lock: debug

Postgres 15

• test_empty_branch_remote_storage_upload: debug

Code coverage* (full report)

• functions: 28.0% (6600 of 23537 functions)
• lines: 46.7% (46860 of 100326 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
ed0199a at 2024-05-01T22:10:53.767Z :recycle:}

[tristan957]

Can you add info into the commit description about why this commit exists? Seems like you added some good info in the PR description.

[save-buffer]

Won't the PR description get put into the commit that gets merged into main?

[tristan957]

Won't the PR description get put into the commit that gets merged into main?

Depends how you merge it :)

[save-buffer]

I have used the squash and merge button, just how you like it!