api: Update pending block treatment

[tnasu]

Proposed changes

Change the behavior of APIs when "pending" is given as an rpc.BlockNumber parameter.

1. Remove support for pending logs

• Following single-shot APIs do not accept "pending" as a block number parameters fromBlock nor toBlock.
  • eth_getLogs, kaia_getLogs (src)
  • eth_newFilter, kaia_newFilter (src)
• Following subscription APIs do not scan pending blocks when requested with "logs" event type (src) (docs)
  • eth_subscribe, kaia_subscribe
• Users who have been using "pending" must now use "latest" for single-shot APIs for the same result.
• Note that for ENs and PNs the behavior won't change as they don't mine blocks, thus pending block equals latest block.

2. Add support for pending blocks for feehistory and recover APIs

• Following APIs, in CN, will now utilize currently mining block when given "pending" as a block argument.
  • eth_feeHistory, kaia_feeHistory (src)
  • kaia_recoverFromTransaction (src)
• Users can keep using "pending" argument.
• In EN and PN these APIs will behave the same. Pending block equals latest block.

3. Do not return error from simple query APIs

• Following APIs no longer return error upon missing data. Instead they return null.
  • eth_getBlockTransactionCountByNumber, kaia_getBlockTransactionCountByNumber
  • eth_getBlockTransactionCountByHash, kaia_getBlockTransactionCountByHash
  • eth_getTransactionByBlockNumberAndIndex, kaia_getTransactionByBlockNumberAndIndex
  • eth_getTransactionByBlockHashAndIndex, kaia_getTransactionByBlockHashAndIndex
  • eth_getRawTransactionByBlockNumberAndIndex, kaia_getRawTransactionByBlockNumberAndIndex
  • eth_getRawTransactionByBlockHashAndIndex, kaia_getRawTransactionByBlockHashAndIndex
• Users might need to handle the null result.

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 read the CLA and signed by comment I have read the CLA Document and I hereby sign the CLA in first time contribute
• Lint and unit tests pass locally with my changes ($ make test)
• 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

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