[MDEV-12199] Split Item_func_{abs|neg|int_val}::fix_length_and_dec() into methods in Type_handler - Jira

The following methods:

Item_func_neg::fix_length_and_dec()

Item_func_abs::fix_length_and_dec()

Item_func_int_val::fix_length_and_dec()

have switches on arg[0]->cast_to_int_type().
This is not friendly to pluggable data types.

Under term of this task we'll split implementations of these methods into new methods in Type_handler:

virtual bool Item_func_abs_fix_length_and_dec(Item_func_abs *) const;

virtual bool Item_func_int_val_fix_length_and_dec(Item_func_int_val *) const;

virtual bool Item_func_neg_fix_length_and_dec(Item_func_neg *) const;

blocks

MDEV-4912 Add a plugin to field types (column types)