Trivial changes for dynamic base fee

[jimni1222]

Proposed changes

This PR includes small changes before implementation dynamic base fee in common architecture.

• Added getHeader rpc call for caver.klay.accounts (before common architecture feature)
• Implement _getSuggestedGasPrice for internal usage when sign via caver.klay.accounts (before common architecture feature)
• Added caver.rpc.net.getVersion to RPC layer
• Added effectiveGasPrice field to TransactionReceipt type
• Modified mistypo

Types of changes

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• Bugfix
• New feature or enhancement
• Others

Checklist

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• I have read the CONTRIBUTING GUIDELINES doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

Related issues

related to #662

Further comments

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