Auto generate record ID class if no explicit `@IdClass`

Given an entity meets:
1. using composite primary key
2. no `@IdClass` annotated

For example:
```java
@Entity
public class Employee {
@Id String empName;
@Id Date birthDay;
...
}
```
It would be convenient if a record class is generated as implicit `@IdClass`
```java
public record EmployeeId(String empName, Date birthDay) {}
```
candidate names of generated record class:
- EmployeeId
- EmployeePK
- EmployeeId_
- EmployeePK_
- Employee$Id
- Employee$PK

No implementation files, tests, or entry points are named. Start by reviewing the composite-key example and the proposed record-class names, then determine the specification and implementation scope. Done means entities with composite primary keys and no explicit @IdClass receive a consistent implicit record class.

Written by the indexing model from the issue text.