[pallet-revive] implement the gas limit API (#6926)
This PR implements the gas limit API, returning the maximum ref_time per block. Solidity contracts only know a single weight dimension and can use this method to get the block ref_time limit. --------- Signed-off-by: Cyrill Leutwiler <[email protected]> Signed-off-by: xermicus <[email protected]> Co-authored-by: command-bot <>