Add more convenience methods to PersistenceConfiguration

I found there only provides a `managedClass(Class class)` method in the [`PersistenceConfiguration`](https://github.com/jakartaee/persistence/blob/master/api/src/main/java/jakarta/persistence/PersistenceConfiguration.java), but does not provides methods to add a collection of classes.

eg.

```java
PersistenceConfiguration managedClasses(Class classes...)
PersistenceConfiguration managedClasses(Collection> classes)

// add all jpa managed classes in the package located by the specified class
PersistenceConfiguration managedPackage(Class class)
PersistenceConfiguration managedPackages(Class classes...)
PersistenceConfiguration managedPackages(Collection> classes)
```

Start with api/src/main/java/jakarta/persistence/PersistenceConfiguration.java and review the existing managedClass(Class class) method. Clarify the intended behavior and API conventions for collection, varargs, and package-management methods; the work is done when the agreed convenience methods are defined with consistent behavior.

Written by the indexing model from the issue text.