Add util method to component graph to get components based on component class

[angela97lin]

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Right now, component_graph.get_component expects a string which is the unique name used to find a component in the graph (ex: "My Label Encoder", and not "Label Encoder"). This makes it difficult to find components of a specific class, ex LabelEncoder instances. We should add a method to help with this!

API should take into consideration what happens if we have multiple of the same component in a graph. Ex: if we have two label encoders under "LE 1" and "LE 2", we should find both.