storcon: do timeline creation on all attached location

[VladLazar]

Problem

Creation of a timelines during a reconciliation can lead to unavailability if the user attempts to
start a compute before the storage controller has notified cplane of the cut-over.

Summary of changes

Create timelines on all currently attached locations. For the latest location, we still look
at the database (this is a previously). With this change we also look into the observed state
to find other attached locations.

Related #9144

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]

5111 tests run: 4904 passed, 0 failed, 207 skipped (full report)

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Flaky tests (6)

Postgres 17

• test_ondemand_wal_download_in_replication_slot_funcs: release-x86-64

Postgres 15

• test_multixid_wraparound_import: release-x86-64
• test_subscriber_restart: release-x86-64
• test_timeline_ancestor_detach_errors[True]: release-x86-64

Postgres 14

• test_isolation[4]: release-arm64
• test_restart_endpoint_after_switch_wal: release-x86-64

Code coverage* (full report)

• functions: 31.3% (7491 of 23896 functions)
• lines: 49.5% (60123 of 121438 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
985de0c at 2024-10-03T11:53:34.556Z :recycle:}