Use implicit join to create Predicate if possible

[quaff]

Fix GH-3349

[quaff]

It should mitigate GH-3274 and GH-3307 also.

[christophstrobl]

Thank you @quaff! Would you mind adding some tests to verify the behaviour?

[quaff]

Thank you @quaff! Would you mind adding some tests to verify the behaviour?

I'm trying.

[quaff]

Thank you @quaff! Would you mind adding some tests to verify the behaviour?

I'm trying.

@christophstrobl Done!

[quaff]

see https://docs.jboss.org/hibernate/orm/current/userguide/html_single/Hibernate_User_Guide.html#hql-implicit-join

[quaff]

There is a subtle change by this PR, since implicit join will use inner join, then IS_NULL will require ManyToOne relation entity exists but property of that entity is null, before this commit, it imply relation entity is null or property of entity is null. It's easy to keep the behavior as before, but I doubt it's right to do that.