MLIR: cut a constant predicate column under a skip and a limit

[rjb32]

A comparison or boolean operation over constants folds to a ColumnConst, so the skip and limit truncates now pick their copy family from the column rather than from the operation, which only recognised arithmetic.

RETURN 1 < 2
RETURN true and false
RETURN 1 < 2 SKIP 0 LIMIT 1
RETURN true and false SKIP 0 LIMIT 1
RETURN not true SKIP 0 LIMIT 1
RETURN 1 < 2 LIMIT 1
RETURN 1 < 2 SKIP 0
RETURN 1 < 2 SKIP 1
RETURN 1 < 2 SKIP 1 LIMIT 1
RETURN true and false SKIP 0 LIMIT 0
RETURN 1 < 2, true and false SKIP 0 LIMIT 1