Do not render Exist() Predicates on join keys Filters

[Hor911]

Because they have little to nothing useful for user

Currently

│          -> Filter (Predicate: Exist(item.n.n_regionkey))
│            -> InnerJoin (Grace) (Condition: 0,1 = 0,1)
│              -> Filter (Predicate: Exist(item.c.c_nationkey) And Exist(item.s.s_nationkey))
│                -> InnerJoin (Grace) (Condition: 0 = 0)
│                  -> Filter (Predicate: Exist(item.l.l_suppkey))
│                    -> InnerJoin (Grace) (Condition: 0 = 0)
│                      -> Filter (Predicate: Exist(item.o.o_orderkey))
│                        -> InnerJoin (Grace) (Condition: 0 = 0)

Proposed

│            -> InnerJoin (Grace) (Condition: 0,1 = 0,1)
│                -> InnerJoin (Grace) (Condition: 0 = 0)
│                    -> InnerJoin (Grace) (Condition: 0 = 0)
│                        -> InnerJoin (Grace) (Condition: 0 = 0)

(join keys should be added into InnerJoin line instead of indices, and it is separate issue)