Add scheduling_policy column to safekeepers table

[arpad-m]

Add a scheduling_policy column to the safekeepers table of the storage controller.

Part of #9981

[github-actions]

7260 tests run: 6896 passed, 0 failed, 364 skipped (full report)

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Flaky tests (1)

Postgres 15

• test_physical_replication_config_mismatch_max_locks_per_transaction: release-arm64

Code coverage* (full report)

• functions: 31.1% (8411 of 27042 functions)
• lines: 47.8% (66840 of 139865 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
c94a566 at 2025-01-09T15:50:41.612Z :recycle:}