Function normalize_first_column 

fn normalize_first_column(
    value: &VariableValue,
    value_len: u32,
    bit_width: u32,
) -> Result<VariableValue, MappingParseError>

Normalize the first column value according to its type and specified bit width.

• Check that numeric values fit within the specified bit width.
• Check that strings fit within the specified bit width and extend them if they are shorter.
• Convert string values that are binary strings to numeric values.