The binary literal default value is not handled correctly

[YangKeao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

func TestBitDefaultValue(t *testing.T) {
	store := testkit.CreateMockStore(t)
	tk := testkit.NewTestKit(t, store)
	tk.MustExec("use test")
	tk.MustExec("create table t(a bit(32) default b'1100010001001110011000100100111')")
	tk.MustExec("insert into t values ()")
	tk.MustQuery("select hex(a) from t").Check(testkit.Rows("62273127"))
}

It's because b'1100010001001110011000100100111' is converted to "b'1'", and then casted to 1.

2. What did you expect to see? (Required)

The test passed

3. What did you see instead (Required)

The test failed

4. What is your TiDB version? (Required)

mysql> select tidb_version();
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                      |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v8.4.0-this-is-a-placeholder
Edition: Community
Git Commit Hash: None
Git Branch: None
UTC Build Time: None
GoVersion: go1.23.2
Race Enabled: false
Check Table Before Drop: false
Store: unistore |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[YangKeao]

Also, the following DDL didn't produce an error:

create table t(a bit(1) default b'1100010001001110011000100100111')