MDEV-23351 Rounding functions return wrong data types for DATE input

Fixing ROUND(date,0), TRUNCATE(date,x), FLOOR(date), CEILING(date)
to return the `int(8) unsigned` data type.

Details:
1. Cleanup: moving virtual implementations
   - Type_handler_temporal_result::Item_func_int_val_fix_length_and_dec()
   - Type_handler_temporal_result::Item_func_round_fix_length_and_dec()
   to Type_handler_date_common. Other temporal data type handlers
   override these methods anyway. So they were only DATE specific.
   This change makes the code clearer.
2. Backporting DTCollation_numeric from 10.5, to reuse the code easier.
3. Adding the `preferred_attrs` argument to Item_func_round::fix_arg_int(). Now
   Type_handler_xxx::Item_func_round_val_fix_length_and_dec() work as follows:
   - The INT-alike and YEAR handlers copy preferred_attrs from args[0].
   - The DATE handler passes explicit attributes, to get `int(8) unsigned`.
   - The hex hybrid handler passes NULL, so fix_arg_int() calculates attributes.
4. Type_handler_date_common::Item_func_int_val_fix_length_and_dec()
   now sets the type handler and attributes to get `int(8) unsigned`.

1 files changed, 6 insertions, 3 deletions

diff --git a/sql/item_func.cc b/sql/item_func.cc
index 8e36804888b..6b19933fd48 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -2455,13 +2455,16 @@ void Item_func_round::fix_arg_datetime()
                           (without extending to DECIMAL).
                           - If `preferred` is not NULL, then the code tries
                             to preserve the given data type handler and
-                            data type attributes of the argument.
+                            the data type attributes `preferred_attrs`.
                           - If `preferred` is NULL, then the code fully
                             calculates attributes using
                             args[0]->decimal_precision() and chooses between
                             INT and BIGINT, depending on attributes.
+  @param [IN] preferred_attrs - The preferred data type attributes for
+                                simple cases.
 */
-void Item_func_round::fix_arg_int(const Type_handler *preferred)
+void Item_func_round::fix_arg_int(const Type_handler *preferred,
+                                  const Type_std_attributes *preferred_attrs)
 {
   DBUG_ASSERT(args[0]->decimals == 0);
   if (args[1]->const_item())
@@ -2477,7 +2480,7 @@ void Item_func_round::fix_arg_int(const Type_handler *preferred)
       int length_can_increase= MY_TEST(!truncate && val1.neg());
       if (preferred)
       {
-        Type_std_attributes::set(args[0]);
+        Type_std_attributes::set(preferred_attrs);
         if (!length_can_increase)
         {
           // Preserve the exact data type and attributes