fix(pageserver): LSN lease edge cases around restarts/migrations

[yliang412]

Part of #7497, closes #8817.

Problem

See #8817.

Summary of changes

compute_ctl

• Renew lsn lease as soon as /configure updates pageserver_connstr, use state_changed Condvar for synchronization.

pageserver

• Have separate init_lsn_lease and renew_lsn_lease API. Verify lsn against only on the initial http lease request.

neon_local

• add and call timeline_init_lsn_lease mgmt_api at static endpoint start. The initial lsn lease http request is sent when we run cargo neon endpoint start <static endpoint>.

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]

4968 tests run: 4803 passed, 1 failed, 164 skipped (full report)

---

Failures on Postgres 15

• test_remote_storage_backup_and_restore[True-real_s3]: release-arm64

# Run all failed tests locally:
scripts/pytest -vv -n $(nproc) -k "test_remote_storage_backup_and_restore[release-pg15-True-real_s3]"

Flaky tests (4)

Postgres 17

• test_pageserver_compaction_smoke: release-arm64

Postgres 16

• test_ondemand_wal_download_in_replication_slot_funcs: release-arm64
• test_subscriber_restart: release-x86-64

Postgres 14

• test_subscriber_restart: release-x86-64

Test coverage report is not available

_{The comment gets automatically updated with the latest test results
e7f34ef at 2024-09-19T20:15:43.706Z :recycle:}