Enhancement: Service Load MethodHandles.Lookup

[SentryMan]

When using JPMS, MethodHandles.publicLookup()/MethodHandles.lookup() as currently used by ebean require a user to add an exports my.package directive to allow ebean to access the fields/methods/constructors of entities/DTOs.

The way around this is to pass a MethodHandles.Lookup from the entity/DTO class's module for ebean to use. I'm thinking we could create a new interface:

import java.lang.invoke.MethodHandles.Lookup;

public interface LookupProvider {

  Lookup provideLookup();

}

And have the querybean generator generate an implementation that can be service loaded.

public class Example implements LookupProvider {

  private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup();

  @Override
  public Lookup provideLookup() {
    return LOOKUP;
  }
}

In this way, ebean can gain free reign to access the fields/methods/constructors of entities/DTOs without needing exports/opens directives from the user.

Related to #3530

Would like to get #3528 merged before I start on this