Widgets as map markers won't show up unless it is a simple widget

[vusters]

Widgets used as map marker is currently restricted to very simple widget. It doesn't show up the moment we wrapped it inside a Container (e.g. Row/Stack). It has to do with the current way of taking a snapshot of the Widget to be shown as an image. With wrapped Containers the size will be zero.

[sharjeelyunus]

@vusters please also include the loading time issue for the custom markers as well We're using Avatar, and it takes 30-60 seconds to load the widget, but if we use image instead of widget, it works fine, but there are no styling in the image