In 2.80 screen layouts have been replaced with workspaces. This refers to the entire layout of blenders window.
Using python we can change the active workspace with
nws = bpy.data.workspaces['Animation']
bpy.context.window.workspace = nws
I don't see an operator that allows us to change the workspace in 2.80, at least not without creating a new workspace. That would require writing an addon to add that functionality.
We can change the current editor (the one the cursor is over), to do that we use
To use that in your custom pie menu
row.operator("screen.space_type_set_or_cycle").space_type = 'VIEW_3D'
When using that in the kemap editor, you enter
screen.space_type_set_or_cycle and then choose the editor type in the menu.
You will find within the window group of hotkeys, where you want to add your hotkeys for this, combining ⇧ Shift with F1-F12 is already setup to switch editors. The NLA, Info and Preferences being the editors with no hotkey setup.