[ui] Refactor node pasting using graph partial serialization

Re-implement node pasting by relying on the graph partial serializer,
to serialize only the subset of selected nodes.
On pasting, use standard graph deserialization and import the content
of the serialized graph in the active graph instance.

Simplify the positioning of pasted nodes to only consider mouse position
or center of the graph, which works well for the major variety of use-cases.
Compute the offset to apply to imported nodes by using the de-serialized
graph content's bounding box.

meshroom/core/graph.py

@@ -676,41 +676,6 @@ class Graph(BaseObject):
 
         return duplicates
 
-    def pasteNodes(self, data, position):
-        """
-        Paste node(s) in the graph with their connections. The connections can only be between
-        the pasted nodes and not with the rest of the graph.
-
-        Args:
-            data (dict): the dictionary containing the information about the nodes to paste, with their names and
-                         links already updated to be added to the graph
-            position (list): the list of positions for each node to paste
-
-        Returns:
-            list: the list of Node objects that were pasted and added to the graph
-        """
-        nodes = []
-        with GraphModification(self):
-            positionCnt = 0  # always valid because we know the data is sorted the same way as the position list
-            for key in sorted(data):
-                nodeType = data[key].get("nodeType", None)
-                if not nodeType:  # this case should never occur, as the data should have been prefiltered first
-                    pass
-
-                attributes = {}
-                attributes.update(data[key].get("inputs", {}))
-                attributes.update(data[key].get("outputs", {}))
-                attributes.update(data[key].get("internalInputs", {}))
-
-                node = Node(nodeType, position=position[positionCnt], **attributes)
-                self._addNode(node, key)
-
-                nodes.append(node)
-                positionCnt += 1
-
-            self._applyExpr()
-        return nodes
-
     def outEdges(self, attribute):
         """ Return the list of edges starting from the given attribute """
         # type: (Attribute,) -> [Edge]