[SHELL32] Support IDropTarget handler in IContextMenu static verbs (#5860)

[SHELL32] Support IDropTarget handler in IContextMenu static verbs (#5860)

This adds support for the `DropHandler` subkey in static verbs. `IDropTarget` is called when the verb is invoked. The advantage of this is that no library needs to be loaded until the verb is actually invoked unlike `IContextMenu` shell extensions that have to be loaded during menu creation.

This method is preferred for verb implementations that must work on Windows XP, see
https://learn.microsoft.com/en-us/previous-versions/windows/desktop/legacy/dd940354%28v%3Dvs.85%29?redirectedfrom=MSDN#description