extend eth_call and estimateGas api with state override

[wgr523]

Proposed changes

Extend eth_call and estimateGas api with state override

Types of changes

What types of changes does your code introduce to XDC network?
Put an ✅ in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)
• Regular KTLO or any of the maintaince work. e.g code style
• CICD Improvement

Impacted Components

Which part of the codebase this PR will touch base on,

Put an ✅ in the boxes that apply

• Consensus
• Account
• Network
• Geth
• Smart Contract
• External components
• Not sure (Please specify below)
• API

Checklist

Put an ✅ in the boxes once you have confirmed below actions (or provide reasons on not doing so) that

• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
• N/A

Test plan

I already tested with a local xdc node. And we can also do the same test on devnet/testnet. The plan is as follows.

Run normal eth_call on XDCValidator smart contract's getOwnerCount()

curl http://localhost:8545 -X POST -H "Content-Type: application/json" \
   --data '{"method":"eth_call","params":[{"to":"0x0000000000000000000000000000000000000088","data":"0xef18374a"}, "latest"],"id":1,"jsonrpc":"2.0"}'

Expected result : the number of owner

Test override code:

this fake code should return 0xff: 60ff60005360016000f3, no matter calldata. so you can run

curl http://localhost:8545 -X POST -H "Content-Type: application/json" \
   --data '{"method":"eth_call","params":[{"to":"0x0000000000000000000000000000000000000088","data":"0xef18374a"}, "latest", {"0x0000000000000000000000000000000000000088":{"code":"0x60ff60005360016000f3"}}],"id":1,"jsonrpc":"2.0"}'

Expected result : 0xff

Test override state:

ownerCount is stored at key=000000000000000000000000000000000000000000000000000000000000000a. So we override it with 0x33 (or any random number) and call getOwnerCount().

Use state inside parameter.

curl http://localhost:8545 -X POST -H "Content-Type: application/json" \
   --data '{"method":"eth_call","params":[{"to":"0x0000000000000000000000000000000000000088","data":"0xef18374a"}, "latest", {"0x0000000000000000000000000000000000000088":{"state":{"0x000000000000000000000000000000000000000000000000000000000000000a": "0x0000000000000000000000000000000000000000000000000000000000000033"}}}],"id":1,"jsonrpc":"2.0"}'

or
Use stateDiff inside parameter.

curl http://localhost:8545 -X POST -H "Content-Type: application/json" \
   --data '{"method":"eth_call","params":[{"to":"0x0000000000000000000000000000000000000088","data":"0xef18374a"}, "latest", {"0x0000000000000000000000000000000000000088":{"stateDiff":{"0x000000000000000000000000000000000000000000000000000000000000000a": "0x0000000000000000000000000000000000000000000000000000000000000033"}}}],"id":1,"jsonrpc":"2.0"}'

Expected result : 0x0000000000000000000000000000000000000000000000000000000000000033