Update workflow_fields config page to improve performance

We have an entity that has around 10 bundles with around 100 fields/properties each and the workflow_fields page to configure their permissions can't handle that amount of request to the theme framework and it throws an out of memory error.

The way we found to avoid this was to create an intermediate page after selecting which workflow phase to configure and allow the user to choose which entity type he/she wants to configure and display only the fields/properties for that entity/type pair, reducing the load on the theme framework and avoid the aforementioned memory errors