Expand documentation of error codes for smart contracts

[abizjak]

Task description

There is bare-bones documentation of error codes in https://developer.concordium.software/en/mainnet/smart-contracts/guides/custom-errors.html

What is missing is listing of hard-coded error codes assigned to ParseError, (), NewContractNameError and LogError.

[dg-concordium]

@abizjak Do we have descriptions of these hardcoded error codes somewhere?

[abizjak]

It's this list

Variant	Error code
()	i32::MIN + 1 (-2147483647)
ParseError	i32::MIN + 2 (-2147483646)
LogError::Full	i32::MIN + 3 (-2147483645)
LogError::Malformed	i32::MIN + 4 (-2147483644)
NewContractNameError:://! MissingInitPrefix	i32::MIN + 5 (-2147483643)
NewContractNameError::TooLong	i32::MIN + 6 (-2147483642)
NewContractNameError::ContainsDot	i32::MIN + 9 (-2147483639)
NewContractNameError::InvalidCharacters	i32::MIN + 10 (-2147483638)
NewReceiveNameError::MissingDotSeparator	i32::MIN + 7 (-2147483641)
NewReceiveNameError::TooLong	i32::MIN + 8 (-2147483640)
NewReceiveNameError::InvalidCharacters	i32::MIN + 11 (-2147483637)
NotPayableError	i32::MIN + 12 (-2147483636)