add configurable historical balance health check for finalized block …

[Krish-vemula]

Summary

Adds an optional health check that verifies RPC nodes can access historical blockchain state at finalized blocks.

Changes

New Configuration Options ([EVM.NodePool]):

• HistoricalBalanceCheckEnabled (bool, default: false) - Enables the historical state health check
• HistoricalBalanceCheckAddress (address, default: 0x0...0) - The address used for the eth_getBalance probe

Implementation:

• During RPC node polling (every PollInterval), if enabled, executes eth_getBalance at the finalized block
• For chains with FinalityTagEnabled = true : queries using the "finalized" block tag
• For chains with FinalityTagEnabled = false : queries at latest - FinalityDepth
• Failures count toward PollFailureThreshold - after enough consecutive failures, the node is marked unreachable and traffic fails over to healthy nodes

Configuration Example

[[EVM]]
ChainID = '1'
FinalityTagEnabled = true

[EVM.NodePool]
PollInterval = '10s'
PollFailureThreshold = 5
HistoricalBalanceCheckEnabled = true
HistoricalBalanceCheckAddress = '0x0000000000000000000000000000000000000000'

[github-actions]

⚠️ API Diff Results - Breaking changes detected

📦 Module: github-com-smartcontractkit-chainlink-evm

🔴 Breaking Changes (2)

pkg/config.NodePool (2)

• HistoricalBalanceCheckAddress — ➕ Added

• HistoricalBalanceCheckEnabled — ➕ Added

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