op-reth: acknowledge indexed proof heights

[joshklop]

Proof-history catch-up can currently acknowledge a notification target before the asynchronous engine has indexed it, while temporary parent-state unavailability is treated as successful progress and retried without delay. This keeps FinishedHeight at the engine's actual indexed tip and applies exponential backoff to no-progress attempts, preventing premature replay-data pruning and tight retry loops while allowing catch-up to resume automatically.

Stacked on #23046.

Closes #23105

[joshklop]

Superseded by #23046:

• FinishedHeight is now emitted only for heights the proofs engine has persisted (5ea8578), not for buffered blocks.
• The no-progress StateForHashNotFound -> Ok(()) path no longer exists: execution doesn't need reth's parent-state provider (cfe5c8e). Failed executions return retryable errors that the sync loop backs off on, with a deadline-based retry timer (ed0fc14).

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