Support FDG

[boyuan-chen]

Now we can fully rely on our subgraphs.

We have two functions:

• getLatestFDGSubmittedBlock(chainId) -> It returns the l2 block number of latest FDG game that has been resolved. Any l2 withdrawal transaction before this block number can submit the proof.
  If something goes wrong, it return 0.
• getRootClaimOfFDGSubmission(chainId, blockNumber) -> It returns

{ status: 'success', id: FDG_ADDRESS, rootClaim, l2BlockNumber, index }

given a l2 block number.

If the game has been created or resolved, it returns

{ status: 'error', error:' 'No submission found for the given block number' }

For any other problems, it returns

{ status: 'error', error:' 'Unknown error' }

These issues have been fixed
I am worried about the RPC endpoint.
I am talking with Tenderly to see if there is a way to use their RPC endpoint in our gateway.

[wsdt]

++ on the RPC

[sk-enya]

Changes tested with gateway locally all looks good so merging PR!