Round 2 / metrics

Metrics enable the configuration of alerts to address issues proactively, such as insufficient balance and excessive signature delays. JSON-RPC requests are rate-limited based on token usage, with each token having a set request limit within a fixed period. Exceeding this limit results in request denial, ensuring service protection and maintaining integrity by effectively managing request loads. Overall, our metrics tool greatly enhances the Venus cluster's operational efficiency through robust monitoring, alerting, and protection features.