ot::StringParseUint8() function

Parses a decimal number from a string as `uint8_t` and skips over the parsed characters. If the string does not start with a digit, `kErrorParse` is returned. All the digit characters in the string are parsed until reaching a non-digit character. The pointer `aString` is updated to point to the first non-digit character after the parsed digits. If the parsed number value is larger than @p aMaxValue, `kErrorParse` is returned.