Split LoaderTask.processWorkspaceItem into separate methods.

Right now, processWorkspaceItem is almost impossible to fully
understand. It is a behemoth of a method that handles everything
possibily related to processing a workspace item.

In order to make life easier for developers, it is being split into
smaller methods that deal with limited functionality each, and are
commented / named well. These can also be individually unit tested, so
developers don't have to use mock data anymore to test even the smallest
bit of functionality.

Bug: 318398886
Test: Manually verified that the workspace loading behavior still works
on device.
Flag: None, this is just a copy/paste refactor.

Change-Id: I040bce708cada5b29cf3488ddf37ccc8d7af8282