max_char_length() returns value that is too small for a string returned by FORMAT() with doubles in scientific notation

Consider the example:

MariaDB [test]> CREATE OR REPLACE TABLE t1 AS SELECT FORMAT(1e300,2);

ERROR 1406 (22001): Data too long for column 'FORMAT(1e300,2)' at row 1

There is an assumption that doubles represented as strings couldn't take more then 22 chars. This is incorrect if a big double is sent into FORMAT() function. However the expression args[0]->max_char_length() that is called inside Item_func_format::fix_length_and_dec() returns 22 and this causes the error.

This is also relevant for ColumnStore.