Add retry to fetching basebackup

[save-buffer]

Problem

Currently we have no retry mechanism for fetching basebackup. If there's an unstable connection, starting compute will just fail.

Summary of changes

Adds an exponential backoff with 5 retries to get the basebackup.

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]

2376 tests run: 2261 passed, 0 failed, 115 skipped (full report)

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Flaky tests (5)

Postgres 16

• test_statvfs_pressure_min_avail_bytes: debug

Postgres 15

• test_statvfs_pressure_usage: debug
• test_gc_cutoff: debug
• test_timeline_size_quota_on_startup: release

Postgres 14

• test_statvfs_pressure_usage: debug

Code coverage (full report)

• functions: 54.5% (11224 of 20610 functions)
• lines: 81.5% (63253 of 77648 lines)

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_{The comment gets automatically updated with the latest test results
749d6a8 at 2024-02-01T21:00:49.490Z :recycle:}