[InferReadWrite] Update the heuristic to infer the enable signal

[prithayan]

This commit updates the heuristic to infer the enable signal drivers. Since temporary wires can be introduced by circt passes, the immediate getConnectSrc is not enough to infer the enable signal that might also drive the wmode. Traverse the assignment chain to get all the temporary wires that can potentially drive the enable. Use the set to simplify the write mode expression.