ocaml: phase 5.1 interval_overlap.ml baseline (7 intervals, 6 overlapping pairs)

For each (i, j) pair with i < j, test whether intervals (s1, e1)
and (s2, e2) overlap via the standard `s1 <= e2 && s2 <= e1`.

  intervals: (1,4) (2,5) (7,9) (3,6) (8,10) (11,12) (0,2)

  overlapping pairs:
    (1,4) & (2,5)        (1,4) & (3,6)        (1,4) & (0,2)
    (2,5) & (3,6)        (2,5) & (0,2)
    (7,9) & (8,10)
                                                     = 6

Tests double for-loop with both-side tuple destructure via
`let (s1, e1) = arr.(i) in`, conjunctive comparison, list-to-
array conversion.

188 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -81,6 +81,7 @@
   "histogram_area.ml": 10,
   "huffman.ml": 224,
   "int_sqrt.ml": 1027,
+  "interval_overlap.ml": 6,
   "is_prime.ml": 25,
   "island_count.ml": 5,
   "fizz_classifier.ml": 540,