Support nesting skip scan filters for ORed expressions

The SkipScanFilter can handle expressions of the form:
WHERE (a = 1 OR a = 2) AND (b = 3 OR b = 4)
WHERE a IN (1, 2) AND b IN (3, 4)
WHERE a >= 1 AND a <= 2 AND b >= 3 AND b <= 4

We cannot handle these, though:
WHERE (a = 1 AND b = 3) OR (a = 2 AND b = 4)

These types of OR expressions could be handled by SkipScanFilter if we allowed them to be nested. One top level SkipScanFilter could have two child SkipScanFilters and the top level one would manage incrementing each child filter.