feat: allow configuring the block batch size for contract subscriptions

[arcoraven]

Exposes an env var to configure larger batch sizes for contract subscription jobs. This is useful to reduce the amount of RPC calls and DB writes, at the expense of higher delay for jobs to capture events/receipts.

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PR-Codex overview

This PR focuses on improving the handling of contract subscriptions by optimizing the deletion process and introducing configuration for block querying.

Detailed summary

• Simplified the deleteContractSubscription call in remove-contract-subscription.ts.
• Added CONTRACT_SUBSCRIPTION_BLOCK_RANGE to env.ts for configuring block queries.
• Updated createScheduleSeconds in chain-indexer-registry.ts to use CONTRACT_SUBSCRIPTION_BLOCK_RANGE for scheduling.

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