Simplifying Model data load state management

Instead of maintaining 3 different states, each tied to a subset of data,
maintaing a single state that represents all the data. Individual subset
data is invalidated in rare cases and these invalidates are tightly tied
to the UI. This also allows us to add new data to the model, without worring
about classifying the data into a subset.

Bug: 34112546
Change-Id: Id9cb273de35b79e84a2ef8d6556fcf1e72fb4b75