database: ReadCachedTrieNode leaves a log for the unexpected cases

[ehnuje]

Proposed changes

• When ReadCachedTrieNode receives an error except for dataNotFoundErr, it leaves an error log
• This is to check the unexpected error cases.
• Now, every Klaytn database returns nil, dataNotFoundErr for val, err when it fails to find the data

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• New feature or enhancement
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Further comments

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[ehnuje]

@jeongkyun-oh @yoomee1313 @winnie-byun Please take a look =)