`BIT_XOR` result changes from binary string to integer after materialization

MariaDB returns a binary value for `BIT_XOR(t1.c1)` when the argument is a binary/bit column. When the same expression is evaluated through a materialized derived table (or a temporary table created with `CREATE TEMPORARY TABLE ... AS SELECT`), the result is returned as an integer instead.

The numeric value is unchanged, but the SQL result type and client-visible representation are different. For example, the direct query returns `b'
x8b'`, while the materialized query returns `139`.

This violates the expectation that materializing an equivalent relational subquery preserves the expression's result type. The issue is therefore a MariaDB type-inference/materialization bug candidate, rather than a query syntax error or a value-computation error.

Expected result (binary representation):

```text

b'\\x8b'

b'\\x81'

b'\\x05'

```

Actual result after materialization (integer representation):

```text

139

129

5

```

The values are numerically equivalent (`0x8b = 139`, `0x81 = 129`, `0x05 = 5`), but their SQL types are not equivalent.

How to repeat

```sql

DROP DATABASE IF EXISTS bit_xor_type_test;

CREATE DATABASE bit_xor_type_test;

USE bit_xor_type_test;

CREATE TABLE t (

    id INT PRIMARY KEY,

    b BIT(8),

    v INT

);

INSERT INTO t VALUES

    (1, b'10001011', 7),

    (2, b'10000001', 3),

    (3, b'00000101', 12);

```

Run the grouped aggregate directly:

```sql

SELECT b, BIT_XOR(v) AS x

FROM t

GROUP BY b;

```

A binary-capable client receives:

```text

b'\x05'  12

b'\x81'  3

b'\x8b'  7

```

The first result column has MariaDB protocol type `BIT`.

Now move the source projection into a mergeable CTE:

```sql

WITH cut AS (

    SELECT b, v

    FROM t

)

SELECT b, BIT_XOR(v) AS x

FROM cut

GROUP BY b;

```

The equivalent query returns:

```text

5    12

129  3

139  7

```

The first result column now has protocol type `LONG`.

The derived-table form produces the same changed representation:

```sql

SELECT b, BIT_XOR(v) AS x

FROM (

    SELECT b, v

    FROM t

) AS cut

GROUP BY b;

```