This patch is a cleanup required before refactoring the view layer syncing
process {T73411}.
* Remove FIRSTBASE.
* Remove LASTBASE.
* Remove BASACT.
* Remove OBEDIT_FROM_WORKSPACE.
* Replace OBACT with BKE_view_layer_active_object.
* Replace OBEDIT_FROM_VIEW_LAYER with BKE_view_layer_edit_object.
Reviewed By: mont29
Maniphest Tasks: T73411
Differential Revision: https://developer.blender.org/D15799