Added transformation to remove successive and identical `Quant` nodes in the graph

[nghielme]

Since I used this transformation for Edge SpAIce project, I thought this might be generally useful. Sometimes it happens that the model exported from Brevitas contains repeated Quant nodes. Using this transformation, only one of the two remains in the graph, potentially simplifying to process the graph by other tools used after QONNX, such as hls4ml. I am also not sure if we should add this in the cleanup() or leave it as optional.