executor, types: ON DUPLICATE UPDATE with bit convert to LittleEndian

## Bug Report

### 1. Minimal reproduce step (Required)

create table t (id bigint(20) NOT NULL AUTO_INCREMENT, test_bit bit(64) DEFAULT NULL, PRIMARY KEY(id));

insert into t(id,test_bit) values(1,x'AAFF');

insert into t(id,test_bit) values(1,x'AAFF') on duplicate key update `test_bit`=values(`test_bit`);

select hex(test_bit) from t;

### 2. What did you expect to see? (Required)
select hex(test_bit) from t;
+------------------+
| hex(test_bit) |
+------------------+
| AAFF000000000000 |
+------------------+
1 row in set (0.01 sec)

### 3. What did you see instead (Required)
select hex(test_bit) from t;
+------------------+
| hex(test_bit) |
+------------------+
| FFAA000000000000 |
+------------------+
1 row in set (0.01 sec)

### 4. What is your TiDB version? (Required)

version: release-5.0

+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version() |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v5.0.0-414-g6ca79c09c3-dirty
Edition: Community
Git Commit Hash: 6ca79c09c34ecbda1a49a961c049b477eb8f6a65
UTC Build Time: 2023-01-10 08:47:50
GoVersion: go1.16.10
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.77 sec)

Start by running the reported CREATE TABLE, INSERT, ON DUPLICATE KEY UPDATE, and SELECT HEX statements against the affected TiDB version, then trace the executor/types handling for the duplicate-update assignment of a BIT value. Done means the final HEX output remains AAFF000000000000 rather than reversing the byte order, with regression coverage for this reproduction.

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