[EP ABI] Add Node_GetEpType API (#25350)
Add a new API `Node_GetEpType` to get the EP that the node is assigned
to run on.
This API is needed when porting the plugin TRT EP in `GetCapability`
where ep needs to know whether the subgraph(s) of the control flow node
is assigned to the ep and then to add this control flow op to the
support list.
