Remove ConstantConverter

[bahusoid]

That's quite dumb and not effective class that processes all DotNode nodes in query and tries to parse them as constants (load them via reflection)

Example of query where it's needed:

nhibernate-core/src/NHibernate.Test/Legacy/FooBarTest.cs

Line 4292 in 8f05f67

q = s.CreateQuery("from Foo as f where f.Status = FooStatus.OFF");

Where FooStatus.OFF string is transformed to actual enum value. ContstantConverter tries to convert both f.Status and FooStatus.OFF to constant value

Instead fix existing logic present in DotNode that makes reflection calls and checks only when necessary.