refactor(transform): Single dataset, move conflict check up to lib.Save

[dustmop]

Instead of a pair of read/write datasets on the starlark ds object, have only a single dataset. For checking conflicts, have Apply track which components are modified by a transform script. Compare that result against the components provided to the save path, but do so in a much more obvious way, up in lib/

[dustmop]

Ok, now switched to using PathMap to get the components that exist in the incoming dataset. Switched the changeSet (previously changeList) to use full component names now, which removes the need for the shortNameToComponent function.