DEPR: Remove aliased Resampler methods
It seems the forward and backward filling methods are duplicated for Resampler objects (e.g., bfill is an alias for backfill, and ffill is an alias for pad). Does it make sense to deprecate backfill and pad in favor of the bfill and ffill, as these names are more consistent with other methods in pandas (e.g., DataFrame.ffill)?