feat(cheatcodes): add JSON / TOML parsing with default fallbacks

[tynes]

It would be really convenient to be able to set default values in the JSON parsing helpers with a third argument that return the default value when the key is not present in the passed in JSON string.

An example:

readBytes32(string memory json, string memory key, bytes32 default);

This would be similar to the UX of vm.envOr which reads an env var and then returns the default value if it doesn't exist. I am not particular about using overloading or following the Or suffix naming scheme. This would prevent parsing errors for when keys are not present in the JSON. I think it could be implemented by wrapping the low level vm JSON calls with try/catch

[mds1]

@klkvr @mattsse In the spirit of #3782, any objections to adding these overloads as native cheats first, then updating StdJson.sol to have the appropriate read* wrapper methods?

[klkvr]

yep, it makes sense

[tynes]

We are currently using the following implementation

    function _readOr(string memory json, string memory key, uint256 defaultValue) internal view returns (uint256) {
        return vm.keyExists(json, key) ? stdJson.readUint(json, key) : defaultValue;
    }

So not super opinionated on this needing to be a native cheat or not

[mds1]

foundry-rs/forge-std#605 will add this functionality to forge-std, but without the native cheats. Therefore I transferred this issue to the upstream foundry repo. Once the native cheats are added we can simply replace the implementations of the new methods in StdJson and StdToml libraries