feat(isthmus): support EXISTS and UNIQUE set predicates

[nielspardon]

Should be merged after #353 since it shares the same test infrastructure.

Currently, the Substrait to Calcite mappings do not support exists and unique set predicates like the follow SQL example from TPC-H query no. 4:

select
  o.o_orderpriority,
  count(*) as order_count
from
  "orders" o

where
  o.o_orderdate >= date '1996-10-01'
  and o.o_orderdate < date '1996-10-01' + interval '3' month
  and
  exists (
    select
      *
    from
      "lineitem" l
    where
      l.l_orderkey = o.o_orderkey
      and l.l_commitdate < l.l_receiptdate
  )
group by
  o.o_orderpriority
order by
  o.o_orderpriority

This PR adds support for mapping exists and unique set predicates from Substrait into Calcite and adds a test case showing that it works now.

[vbarua]

Looks good overall. Left one minor usability improvment.