XOR incorrectly treats a non-integer string operand as FALSE

1. 1. 1. Summary

MariaDB evaluates the non-integer string `'0.7'` as TRUE in IS TRUE, AND, and OR expressions, but evaluates it as FALSE when it is used as the left operand of XOR.

This can cause rows to be incorrectly filtered out by a WHERE clause.

1. 1. 1. Steps to reproduce

Run the following query:

```sql
SELECT
'0.7' IS TRUE AS is_true,
'0.7' AND TRUE AS and_true,
'0.7' OR FALSE AS or_false,
'0.7' XOR FALSE AS xor_false,
'0.7' XOR TRUE AS xor_true;

1. 1. 1. Expected result
         According to the logical XOR semantics, a non-zero operand is TRUE.
         Therefore:
         '0.7' IS TRUE -> 1
         '0.7' AND TRUE -> 1
         '0.7' OR FALSE -> 1
         '0.7' XOR FALSE -> 1
         '0.7' XOR TRUE -> 0
         The filtering query should return one row:
         -------

         value

         -------

         0.7

         -------

1. 1. 1. Actual result on MariaDB 12.3.2
         -------------------------------------------

         is_true

         and_true

         or_false

         xor_false

         xor_true

         -------------------------------------------

         1

         1

         1

         0

         1

         -------------------------------------------
         The filtering query returns:Empty set
         Thus, MariaDB treats '0.7' as TRUE for IS TRUE, AND, and OR, but as FALSE for XOR.

MySQL 8.0.46 and MySQL 8.4.7 return:
-------------------------------------------

-------------------------------------------

-------------------------------------------
The filtering query also returns one row on both MySQL versions.