Setting EntityType.BaseType does not throw if Child property duplicates new parent property

[mikary]

The following test will fail to throw the expected exception:

        [Fact]
        public void Setting_base_type_throws_when_child_and_parent_contain_duplicate_property()
        {
            var model = new Model();

            var a = new EntityType(typeof(A), model);
            a.AddProperty("E", typeof(string));
            a.AddProperty("G", typeof(string));

            var b = new EntityType(typeof(B), model);

            var c = new EntityType(typeof(C), model);
            c.AddProperty("E", typeof(string));
            c.AddProperty("G", typeof(string));
            c.BaseType = b;

            Assert.Throws<InvalidOperationException>(() => b.BaseType = a);
        }

Property duplication checks currently propagate through an OnPropertyMetadataChanged event. Fixing this issue will probably require a different factoring.