RNA: Object.select_set use boolean, only select

- Was setting active state, making it necessary to backup/restore
  active object in cases where this isn't needed.
  Existing scripts are explicitly setting the active object when needed.

- Use a boolean select arg (toggle selection wasn't used anywhere).

- Add an optional view layer argument since scripts should be able to
  operate outside the user context.

doc/python_api/examples/bpy.types.Object.py

@@ -25,5 +25,5 @@ view_layer.active_layer_collection.collection.objects.link(light_object)
 light_object.location = (5.0, 5.0, 5.0)
 
 # And finally select it and make it active.
-light_object.select_set('SELECT')
+light_object.select_set(True)
 view_layer.objects.active = light_object