Update validator refresh interval

[hyeonLewis]

Proposed changes

This PR updates the validator refresh interval to 1 block, which is currently approx. 1 day (= 86,400 blocks). The validator set at block N now will be determined by staking info at block N-1 if N is Kaia fork block.

Since the Kaia fork, the multicall contract will also be activated. Please check #2158 to know what multicall is and how it works with this.

The snap sync mode will be temporary disabled due to issue related to staking info sync.

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• Bugfix
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