move splot code to giddy

[martinfleis]

This moves code that now lives in spot directly to giddy due to the planned sunsetting of splot. So far it is mostly copy&paste with minor modification of import paths.

A main question I have is what do you want to do with the functions that are not exposed as Rose methods now. Should I expose all or do you want to keep them separately as functions in a public plotting module?

[jGaboardi]

cc @weikang9009

[weikang9009]

I think it is a good idea to expose all plotting functionalities as Rose methods, similar to what was previously done for the two plotting functionalities (dynamic_lisa_rose as plot and dynamic_lisa_vectors as plot_vectors). Any thoughts @sjsrey ?