Add new animation TraceColor (Name for debate) and Graph.set_edge_color()

[MrDiver]

This PR adds some functionality which should simplify the usage of Graphs and animating the edges.

• A function get_edge() now returns the Edge no matter if it is flipped or not. But only for Graph not for DiGraph
• An Animation named TraceColor now exists which can smoothly transition from one color to another over a shape
• set_edge_color on GenericGraph is overriden with an Animation such that it produces a TraceColor effect when animating edge colors.

class SetEdgeColor(Scene):
    def construct(self):
        g = Graph(vertices=[1,2,3], edges=[(1,2), (2,3), (3,1)])
        self.add(g)
        self.play(AnimationGroup((g.animate.set_edge_color((u,v), RED) for u,v in g.edges), lag_ratio=0.5))

SetEdgeColor.mp4

Where TraceColor itself has the following behavior

TraceColorExample.mp4

There are still some problems with the z_indices of objects in the graph but the concept works

[JasonGrace2282]

I like the animation idea!
Left some comments and questions on the implementation. Additionally, it would be nice to add some tests to make sure the methods are working properly.

[JasonGrace2282]

Is there a reason VMobject is in quotations?

[JasonGrace2282]

Suggested change

self.mobject: VMobject

Is this neccessary?

[JasonGrace2282]

Might be a good idea to add a warning either in the code (via logger.warning) or in the docstring about DiGraph.
Same for the part below saying "this will not work on DiGraph"

[JasonGrace2282]

Suggested change

	return self._edges[edge]
	return self.edges[edge]

Typo?

[JasonGrace2282]

Suggested change

	self.edges = {}
	self.edges: dict[tuple[Hashable, Hashable], Mobject] = {}

This way linters can raise errors about setting/getting stuff from this attribute.