clean up json length parsing

[tynes]

If you are open to enabling ffi, it is possible to use jq to get the length of a JSON array. It would allow for the removal of this code:

superchain-ops/src/JsonTxBuilderBase.sol

Lines 24 to 25 in 2b033ba

	// A hacky way to get the total number of elements in a JSON
	// object array because Forge does not support this natively.

There is a lot of usage of jq in the monorepo forge scripts.

Also the solidity team has talked about removing abi.encodePacked in a future version of solidity, so string.concat should be preferred over string(abi.encodePacked(...))

superchain-ops/src/JsonTxBuilderBase.sol

Line 33 in 2b033ba

try vm.parseJsonAddress(json, string(abi.encodePacked("$.transactions[", vm.toString(i), "].to"))) returns (address) {