PR-Codex overview

This PR focuses on updating the cron scheduling implementation in the codebase by replacing the node-cron package with the cron package. It also introduces new environment variable configurations for cron schedules.

Detailed summary

• Added cron package dependency.
• Removed node-cron package dependency.
• Updated type definitions from cron.ScheduledTask to CronJob.
• Refactored scheduling logic in clear-cache-cron.ts and chain-indexer-listener.ts to use the new CronJob class.
• Introduced a new environment variable CONTRACT_SUBSCRIPTION_CRON_SCHEDULE_OVERRIDE.
• Updated INDEXER_REGISTRY to store CronJob instances.
• Simplified the createScheduleSeconds function to accept only blockTimeSeconds.

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