The generated encrypted column is too long

## Bug Report

### Which version of ShardingSphere did you use?
master 3bb9a429

### Which project did you use? ShardingSphere-JDBC or ShardingSphere-Proxy?
all

### Expected behavior
Create table successfully.

### Actual behavior
In MySQL:
```java
java.sql.SQLSyntaxErrorException: Specified key was too long; max key length is 3072 bytes
```

### Reason analyze (If you can)
#27605 The generated encrypted column is too long, which leads to the inability to index.

### Steps to reproduce the behavior, such as: SQL to execute, sharding rule configuration, when exception occur etc.
```sql
-- Logic SQL:
CREATE TABLE t1 (
id int NOT NULL auto_increment PRIMARY KEY,
b int NOT NULL,
c datetime NOT NULL,
INDEX idx_b(b),
INDEX idx_c(c)
) ENGINE=InnoDB
-- Actual SQL:
CREATE TABLE t1 (
id int NOT NULL auto_increment PRIMARY KEY,
b_cipher VARCHAR(4000),
c_cipher VARCHAR(4000),
INDEX idx_b(b_cipher),
INDEX idx_c(c_cipher)
) ENGINE=InnoDB
```

Start by running the provided MySQL CREATE TABLE reproduction and compare the Logic SQL with the Actual SQL generated for encrypted columns. Trace the encrypted-column generation path and verify the fix by confirming that indexed encrypted columns stay within MySQL's key-length limit and the table is created successfully.

Written by the indexing model from the issue text.