Query: DbSet may not be EntityQueryable

[smitpatel]

In test

public void Non_generic_ExecuteQuery_does_not_throw()
        {
            var context = new TestContext();
            Func<IQueryable<TestEntity>, int> func = Queryable.Count;
            IQueryable q = context.TestEntities;
            var expr = Expression.Call(null, func.GetMethodInfo(), Expression.Constant(q));
            Assert.Equal(0, q.Provider.Execute<int>(expr));
            Assert.Equal(0, (int)q.Provider.Execute(expr));
        }

Here the ConstantExpression generated for context.TestEntities is not an EntityQueryable. WIth optimization going in #11030 we now try to parametrize all queryables which not EntityQueryable, which cause this test to fail with A second operation started error.

After discussing with @ajcvickers

• Is it possible to have DbSet type without being of EntityQueryable type?
  • Yes => Then we need to pattern match exclude this case from being funcletized.
  • No => Then we need to fix so that query starting from DbSet already creates EntityQueryable inside Expression tree.