add set_col_def to lod_grid

[WolfgangFahl]

def set_column_def(self, col: str, key: str, value: Any) -> Dict:
        """
        Set a value in a column definition dictionary for a specified column.

        This method updates the column definition dictionary for a given column by
        setting a specific key to a provided value. If the column definition exists,
        the key-value pair is updated; if not, no changes are made.

        Parameters:
            col (str): The name of the column to update.
            key (str): The key in the column definition dictionary to set.
            value (Any): The value to assign to the key in the dictionary.

        Returns:
            Dict: The updated column definition dictionary, or None if the column does not exist.
        """
        col_def = self.get_column_def(col)  # Assuming get_column_def is defined elsewhere.
        if col_def:
            col_def[key] = value
        return col_def