MDEV-11361 Equal condition propagation does not work for DECIMAL and temporal dynamic SQL parameters

MDEV-16426 Optimizer erroneously treats equal constants of different formats as same
A cleanup for MDEV-14630: fixing a crash in Item_decimal::eq().

Problems:
- old implementations of Item_decimal::eq() and
  Item_temporal_literal::eq() were not symmetric
  with Item_param::eq(), this caused MDEV-11361.

- old implementations for DECIMAL and temporal data types
  did not take into account that in case when eq() is called
  with binary_cmp==true, {{eq()}} should check not only equality
  of the two values, but also equality if their decimal precision.
  This cuases MDEV-16426.

- Item_decimal::eq() crashes with "item" pointing
  to a non-DECIMAL value. Before MDEV-14630
  non-DECIMAL values were filtered out by the test:
    type() == item->type()
  as literals of different types had different type().
  After MDEV-14630 type() for literals of all data types return CONST_ITEM.
  This caused failures in tests:
    ./mtr engines/iuds.insert_number
    ./mtr --ps --embedded main.explain_slowquerylog
  (revealed by buildbot)

The essence of the fix:
Making literals and Item_param reuse the same code to avoid
asymmetries between Item_param::eq(Item_literal) and
Item_literal::eq(Item_param), now and in the future, and to
avoid code duplication between Item_literal and Item_param.
Adding tests for "decimals" for DECIMAL and temporal data types,
to treat constants of different scale as not equal when "binary_cmp"
is "true".

Details:
1. Adding a helper class Item_const to extract constant values from Items easier
2. Deriving Item_basic_value from Item_const
3. Joining Type_handler::Item_basic_value_eq() and Item_basic_value_bin_eq()
   into a single method with an extra "binary_cmp" argument
   (it looks simple this way) and renaming the new method to Item_const_eq().
   Modifying its implementations to operate with
   Item_const instead of Item_basic_value.
4. Adding a new class Type_handler_hex_hybrid,
   to handle hex constants like 0x616263.
5. Removing Item::VARBIN_ITEM and fixing Item_hex_constant to
   use type_handler_hex_hybrid instead of type_handler_varchar.
   Item_hex_hybrid::type() now returns CONST_ITEM, like all
   other literals do.
6. Move virtual methods Item::type_handler_for_system_time() and
   Item::cast_to_int_type_handler() from Item to Type_handler.
7. Removing Item_decimal::eq() and Item_temporal_literal::eq().
   These classes are now handled by the generic Item_basic_value::eq().
8. Implementing Type_handler_temporal_result::Item_const_eq()
   and Type_handler_decimal_result::Item_const_eq(),
   this fixes MDEV-11361.
9. Adding tests for "decimals" into
   Type_handler_decimal_result::Item_const_eq() and
   Type_handler_temporal_result::Item_const_eq()
   in case if "binary_cmp" is true.
   This fixes MDEV-16426.
10. Moving Item_cache out of Item_basic_value.
   They share nothing. It simplifies implementation
   of Item_basic_value::eq(). Deriving Item_cache
   directly from Item.

11. Adding class DbugStringItemTypeValue, which
    used Item::print() internally, and using
    in instead of the old debug printing code.
    This gives nicer output in func_debug.result.

Changes N5 and N6 do not directly relate to the bugs fixed,
but make the code fully symmetric across all literal types.
Without a new handler Type_handler_hex_hybrid we'd have
to keep two code branches (for regular literals and for
hex hybrid literals).

mysql-test/main/func_debug.test

@@ -499,19 +499,6 @@ EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a BETWEEN -1 AND ?' USING 184467440737
 EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a BETWEEN -1 AND ?' USING 18446744073709551616;
 DROP TABLE t1;
 
-
-# DECIMAL does not work yet
-CREATE TABLE t1 (a DECIMAL(10,3));
-INSERT INTO t1 VALUES (1),(2),(3);
-SELECT * FROM t1 WHERE a BETWEEN 1.0 AND 1.0;
-DROP TABLE t1;
-
-# Temporal types do not work yet
-CREATE TABLE t1 (a TIME);
-INSERT INTO t1 VALUES ('00:00:00'),('00:00:01');
-SELECT * FROM t1 WHERE a BETWEEN TIME'00:00:00' AND TIME'00:00:00';
-DROP TABLE t1;
-
 CREATE TABLE t1 (a VARCHAR(10));
 INSERT INTO t1 VALUES ('0'),('1'),('2');
 SELECT * FROM t1 WHERE a BETWEEN '0' AND '0';
@@ -520,3 +507,51 @@ SELECT * FROM t1 WHERE a BETWEEN '0' AND '0 ';
 DROP TABLE t1;
 
 SET SESSION debug_dbug="-d,Item_basic_value";
+
+
+--echo #
+--echo # MDEV-11362 True condition elimination does not work for DECIMAL and temporal dynamic SQL parameters
+--echo #
+
+SET SESSION debug_dbug="+d,Item_basic_value";
+
+CREATE TABLE t1 (a DECIMAL(10,3));
+INSERT INTO t1 VALUES (1),(2),(3);
+SELECT * FROM t1 WHERE a BETWEEN 1.0 AND 1.0;
+EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a BETWEEN 1.0 AND ?' USING 1.0;
+DROP TABLE t1;
+
+CREATE TABLE t1 (a TIME);
+INSERT INTO t1 VALUES ('00:00:00'),('00:00:01');
+SELECT * FROM t1 WHERE a BETWEEN TIME'00:00:00' AND TIME'00:00:00';
+EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a BETWEEN TIME''00:00:00'' AND ?' USING TIME'00:00:00';
+DROP TABLE t1;
+
+CREATE TABLE t1 (a DATE);
+INSERT INTO t1 VALUES ('2001-01-01'),('2001-01-02');
+SELECT * FROM t1 WHERE a BETWEEN DATE'2001-01-01' AND DATE'2001-01-01';
+EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a BETWEEN DATE''2001-01-01'' AND ?' USING DATE'2001-01-01';
+DROP TABLE t1;
+
+CREATE TABLE t1 (a DATETIME);
+INSERT INTO t1 VALUES ('2001-01-01 00:00:00'),('2001-01-01 00:00:00');
+SELECT * FROM t1 WHERE a BETWEEN TIMESTAMP'2001-01-01 00:00:00' AND TIMESTAMP'2001-01-01 00:00:00';
+EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a BETWEEN TIMESTAMP''2001-01-01 00:00:00'' AND ?' USING TIMESTAMP'2001-01-01 00:00:00';
+DROP TABLE t1;
+
+SET SESSION debug_dbug="-d,Item_basic_value";
+
+
+--echo #
+--echo # MDEV-16426 Optimizer erroneously treats equal constants of different formats as same
+--echo #
+
+SET SESSION debug_dbug="+d,Item_basic_value";
+
+CREATE TABLE t1 (a VARCHAR(10));
+INSERT INTO t1 VALUES ('a'),('b'),('c');
+SELECT * FROM t1 WHERE a BETWEEN 'a' AND 0x61;
+EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a BETWEEN ''a'' AND ?' USING 0x61;
+DROP TABLE t1;
+
+SET SESSION debug_dbug="-d,Item_basic_value";