Optimize inner loop of intersect union search

Array slice spends a good bit of time allocating memory for new arrays
even for small arrays. For larger computed unions this can be a
non-trivial amount of time. We can minimize the cost by not repeating
the slice for ever iteration of the inner loop since it doesn't depend
on the loop.

src/Type/TypeCombinator.php

@@ -638,11 +638,13 @@ public static function intersect(Type ...$types): Type
 			$topLevelUnionSubTypes = [];
 			$innerTypes = $type->getTypes();
 			usort($innerTypes, $sortTypes);
+			$slice1 = array_slice($types, 0, $i);
+			$slice2 = array_slice($types, $i + 1);
 			foreach ($innerTypes as $innerUnionSubType) {
 				$topLevelUnionSubTypes[] = self::intersect(
 					$innerUnionSubType,
-					...array_slice($types, 0, $i),
-					...array_slice($types, $i + 1),
+					...$slice1,
+					...$slice2,
 				);
 			}