Implement skip connections using the JumpingKnowledge pyg module

[akhilpandey95]

• modify Base class to instantiate pyg.nn.models.JumpingKnowledge
• modify the layer/dimensionality logic to account for concatenated aggregation scheme within JumpingKnowledge
• within Base class include a reset_parameters() to reset skip connection choices
• modify test cases and log the performance of the model on CI test case.

previous issues/PRS

• PR skip connection option added #165
• Issue Skip connection for ResNet type of GNN #164