feat: implement methods for eth_getTransactionByBlockNumberAndIndex and eth_getTransactionByBlockHashAndIndex

[virajbhartiya]

Closes #10640

Proposed Changes

Implement methods for eth_getTransactionByBlockNumberAndIndex and `eth_getTransactionByBlockHashAndIndex

Checklist

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[rvagg]

These should go in api_gateway.go along with the other Eth methods in there - they are reasonable to expose publicly. Once you do that you'll get some compile errors. Go to gateway/proxy_eth.go and have a look at how the methods that take a blkNum argument handle it - you want to checkTipsetHeight at some point, either directly or via checkEthBlockParam--I think we only need the latter if we're supporting the string predefined variants ('latest' etc.) (are we with these?). The main point is that users of the gateway need to be able to set an epoch lookback limit on queires and queries that resolve to tipsets older than that limit should error.

[aarshkshah1992]

@virajbhartiya Reviewed. good stuff.

[virajbhartiya]

@rvagg @aarshkshah1992 I have addressed the above reviews. Both the tests have been merged into one. The EthGetTransactionByBlockNumberAndIndex can now accept either hexadecimal values or "latest", "pending", etc. I have also made the changes in getTransactionByTipsetAndIndex by removing the MsgLookup since the tipset is already there in the list of messages. Thanks for pointing me out to the resources!

[virajbhartiya]

@rvagg @aarshkshah1992 I have addressed the comments above. used Xerrors isntead of fmt. Added rate and lookback limits for both the methods, and added tests for both - SigTypeSecp256k1 and SigTypeBLS messages.

[rvagg]

looking good! almost there, just some minor suggestions left

[rvagg]

all good except for those ErrNullRound inclusions, remove those and we'll merge this

[virajbhartiya]

@rvagg Removed the null round checks for both thee functions

[rvagg]

great work!