KT-49721 Avoid matching from the same position after a zero-width match

In JS, RegExp can return a match before the specified start index,
if it has matched at that index, but it is in the middle of a surrogate
pair. Account for that when advancing to the next position after
a zero-width match so that it doesn't get to the middle of SP.

libraries/stdlib/common/test/testUtils.kt

@@ -18,4 +18,6 @@ public expect val isFloat32RangeEnforced: Boolean
 
 public expect val supportsSuppressedExceptions: Boolean
 
-public expect val supportsNamedCapturingGroup: Boolean
+public expect val supportsNamedCapturingGroup: Boolean
+
+public expect val regexSplitUnicodeCodePointHandling: Boolean