Speed up wrapped collection bounds calculations

[greglucas]

We know they are guaranteed to be the width of the plot, so the bounds for those cells should be much easier to compute than a slow non-affine transform. Perhaps we should override the get_datalim() calculation for that collection...

Originally posted by @greglucas in https://github.com/SciTools/cartopy/issues/1956#issuecomment-986307684