`HoVerNetPostProcessing` to include all branches

[bhashemian]

HoVerNetNuclearTypePostProcessing processes the nuclear type branch and already post-processed output of other branches. Thus for nuclear prediction and hovermap, there is no single post processing transform, and the user should put together 5 different transforms with the right sequence.

It would be great to simplify this process for the user who want to use HoVerNet post processing.

[wyli]

could you please put more details @drbeh

[bhashemian]

could you please put more details @drbeh

done!