MDEV-15957 Unexpected "Data too long" when doing CREATE..SELECT with stored func

Problems:

1. Unlike Item_field::fix_fields(),
  Item_sum_sp::fix_length_and_dec() and Item_func_sp::fix_length_and_dec()
  did not run the code which resided in adjust_max_effective_column_length(),
  therefore they did not extend max_length for the integer return data types
  from the user-specified length to the maximum length according to
  the data type capacity.

2. The code in adjust_max_effective_column_length() was not correct
   for TEXT data, because Field_blob::max_display_length()
   multiplies to mbmaxlen. So TEXT variants were unintentionally
   promoted to the next longer data type for multi-byte character
   sets: TINYTEXT->TEXT, TEXT->MEDIUMTEXT, MEDIUMTEXT->LONGTEXT.

3. Item_sum_sp::create_table_field_from_handler()
   Item_func_sp::create_table_field_from_handler()
   erroneously called tmp_table_field_from_field_type(),
   which converted VARCHAR(>512) to TEXT variants.
   So "CREATE..SELECT spfunc()" erroneously converted
   VARCHAR to TEXT. This was wrong, because stored
   functions have explicitly declared data types,
   which should be preserved.

Solution:

- Removing Type_std_attributes(const Field *)
  and using instead Type_std_attributes::set() in combination
  with field->type_str_attributes() all around the code, e.g.:
     Type_std_attributes::set(field->type_std_attributes())

  These two ways of copying attributes from a Field
  to an Item duplicated each other, and were slightly
  different in how to mix max_length and mbmaxlen.

- Removing adjust_max_effective_column_length() and
  fixing Field::type_std_attributes() to do all necessary
  type-specific calculations , so no further adjustments
  is needed.
  Field::type_std_attributes() is now called from all affected methods:
   Item_field::fix_fields()
   Item_sum_sp::fix_length_and_dec()
   Item_func_sp::fix_length_and_dec()
  This fixes the problem N1.

- Making Field::type_std_attributes() virtual, to make
  sure that type-specific adjustments a properly done
  by individual Field_xxx classes. Implementing
  Field_blob::type_std_attributes() in the way that
  no TEXT promotion is done.
  This fixes the problem N2.

- Fixing Item_sum_sp::create_table_field_from_handler()
  Item_func_sp::create_table_field_from_handler() to
  call create_table_field_from_handler() instead of
  tmp_table_field_from_field_type() to avoid
  VARCHAR->TEXT conversion on "CREATE..SELECT spfunc()".

- Recording mysql-test/suite/compat/oracle/r/sp-param.result
  as "CREATE..SELECT spfunc()" now correctly
  preserve the data type as specified in the RETURNS clause.

- Adding new tests

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 2d47aeb179d..5b4cf075c64 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -1386,7 +1386,7 @@ Item_sum_sp::fix_length_and_dec()
 {
   DBUG_ENTER("Item_sum_sp::fix_length_and_dec");
   DBUG_ASSERT(sp_result_field);
-  Type_std_attributes::set(sp_result_field);
+  Type_std_attributes::set(sp_result_field->type_std_attributes());
   Item_sum::fix_length_and_dec();
   DBUG_VOID_RETURN;
 }