WW-5646 Modernize path normalization in Include component

[arunmanni-ai]

The path normalization logic in Include.getContextRelativePath() used the
legacy java.util.Stack class and did not handle the edge case where
dot-dot segments exceed the available path depth.

This patch:

• Replaces java.util.Stack with ArrayDeque (recommended since JDK 6)
• Adds an isEmpty() guard before pop() to handle excess dot-dot gracefully
• Uses enhanced for-loop instead of indexed elementAt() iteration
• Adds test coverage for edge case dot-dot paths

[arunmanni-ai]

Fixed a regression introduced by the Stack → ArrayDeque swap: the rebuild loop iterated the deque head-to-tail (most recently pushed first), which is the reverse of Stack's insertion-order iteration. This caused rebuilt paths like car/view.jsp to come out as view.jsp/car, which is what the CI failures were catching.

Fixed by using descendingIterator() to restore the original oldest-first ordering when rebuilding the flat path string. The traversal-prevention logic (tokenizing, .. → pop, the isEmpty() guard clamping excess .. at root) is unchanged.

Verified locally — all passed.

[lukaszlenart]

Great, thanks a lot for this patch!