feat(en): Add health checks for EN components

[slowli]

What ❔

Adds health checks with intelligent details for most of components run by the external node.

Why ❔

These health checks would allow monitoring what's going on with an EN easier both for humans and machines. The latter could be used in integration tests etc.

Checklist

• PR title corresponds to the body of PR (we generate changelog entries from PRs).
• Tests for the changes have been added / updated.
• Documentation comments have been added / updated.
• Code has been formatted via zk fmt and zk lint.
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[slowli]

An example of the /health endpoint output for the EN given these changes:

{
  "status": "ready",
  "components": {
    "consistency_checker": {
      "status": "ready",
      "details": {
        "first_checked_batch": 70,
        "last_checked_batch": 80
      }
    },
    "batch_status_updater": {
      "status": "ready",
      "details": {
        "last_committed_l1_batch": 80,
        "last_executed_l1_batch": 80,
        "last_proven_l1_batch": 80
      }
    },
    "http_api": {
      "status": "ready"
    },
    "main_node_http_rpc": {
      "status": "ready"
    },
    "tree": {
      "status": "ready",
      "details": {
        "leaf_count": 24166,
        "mode": "full",
        "next_l1_batch_number": 81,
        "root_hash": "0x40e1bbd383c39c90b9094bbade1040bf7a01cb9f8f892590f5604fe3e0e7d16f",
        "stage": "main_loop"
      }
    },
    "connection_pool": {
      "status": "ready",
      "details": {
        "max_size": 50,
        "pool_size": 11
      }
    },
    "commitment_generator": {
      "status": "ready",
      "details": {
        "l1_batch_number": 80
      }
    },
    "ws_api": {
      "status": "ready"
    },
    "prometheus_exporter": {
      "status": "ready"
    },
    "sync_state": {
      "status": "ready",
      "details": {
        "is_synced": true,
        "local_block": 279,
        "main_node_block": 279
      }
    },
    "reorg_detector": {
      "status": "ready",
      "details": {
        "last_correct_l1_batch": 80,
        "last_correct_miniblock": 279
      }
    }
  }
}