Add ORBPathCallbacksExtended and isExtended flag support

[Kyle-Ye]

Add extended callbacks infrastructure for ORBPath to support callbacks that receive a reference to themselves, enabling nested path operations.

• Add ORBPathCallbacksExtended struct with self-referential callback signatures
• Add ORBPathCallbacksFlags with isExtended flag to distinguish callback types
• Update ORBPathIsEmpty, ORBPathApplyElements, and ORBPathEqualToPath to handle extended callbacks
• Add NestedCallbacks implementation for nested path iteration
• Update compatibility tests for new API