test: Advertise the persistent-data-store-recovery contract test capability

[joker23]

Advertises the new persistent-data-store-recovery contract-test capability (added in launchdarkly/sdk-test-harness#464) from the sync and async contract-test services.

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions
• Sync/async parity: matching changes made to async_* siblings (or N/A)

Related issues

launchdarkly/sdk-test-harness#464

Describe the solution you've provided

• Adds persistent-data-store-recovery to contract-tests/service.py and contract-tests/async_service.py.
• No-op until a harness release containing the recovery suite is picked up by CI.
• The SDK currently fails the new suite (see below) — this should not merge until the SDK fix lands or the failing tests are suppressed.

Describe alternatives you've considered

Suppressing the failing tests in this PR; left out so the failures are visible for review.

Additional context

Local results and root cause

Ran harness PR #464 locally with -enable-persistence-tests -run "persistent data store/.*/store recovery" against Redis (the only store the Python contract service exposes for recovery here).

Sync and async both: 9 ran, 5 failed:

• no cache / infinite cache / ttl cache - writes back full state on recovery
• retries write back after another failure
• recovers from repeated outages

serves updates from memory during outage passes.

Root cause: Store.commit() (ldclient/impl/datasystem/store.py) builds the write-back payload with self._memory_store.all(...), which filters out deleted items. The persistent store is then inited without the tombstone for the deleted flag, while the harness expects the deleted flag to be persisted as a tombstone at the new version. A local experiment that wrote back the memory store's raw items (including tombstones) passed all 9 Redis recovery tests.

Link to Devin session: https://app.devin.ai/sessions/0771b1fabf2b46e093700f45c02dcfff
Open in Devin Desktop: https://app.devin.ai/desktop/session/0771b1fabf2b46e093700f45c02dcfff?variant=devin
Requested by: @joker23

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring