Rearrangable package tags on online wave platform

[aalackner]

Since package order matters when building an image using the online seqera containers tool, it would be useful to be able to move around the packages that have been added to the build before building.

My build had dependency issues and I could solve it by rearranging the order. Now I had to remove everything and add it in the right order but moving them around instead would be a very useful feature.