signTypedData: uint and int fields should be forbidden

[cag]

Right now, signTypedData will accept uint and int, but EIP 712 states that only integer types with their size are allowed.

Trying to use these should error, telling users that uint256 and int256 should be used instead when encountering these types.

[Gudahtt]

Thanks for the report! I agree, but now that signTypedData has been out in the wild for a while, making this change might break dapps.

We might bundle this with a fix for another spec incompatibility that was reported, and ship it as signTypedData_v5