PathSegment.hashCode() threw RuntimeException("Unreachable") for
PathVerb.CLOSE segments when used in hash-based collections such as
intersect(). Added CLOSE case consistent with what equals() checks for
CLOSE segments. Also removed the else branch since all PathVerb values
are now handled. Added a test which fails unless CLOSE is handled in
hashCode().

## Testing
Ran test on awt locally — the new test `closedPathIntersectTest` fails 
before the fix and passes after.

## Release Notes
Fix crash when using closed paths in hash-based collections such as
`intersect()`

Fixes: [SKIKO-1038](https://youtrack.jetbrains.com/issue/SKIKO-1038)