Action Editor WIP: Adding new actions in Action Editor now uses the "stash and create new" operator

In constrast to the old "new" operator, this operator will stash the existing action
in the stack to prevent it from being lost. This situation isn't totally ideal yet,
since the NLA Editor still calls the old method.

release/scripts/startup/bl_ui/space_dopesheet.py

@@ -122,7 +122,7 @@ class DOPESHEET_HT_header(Header):
             dopesheet_filter(layout, context, genericFiltersOnly=True)
 
         if st.mode in {'ACTION', 'SHAPEKEY'}:
-            layout.template_ID(st, "action", new="action.new")
+            layout.template_ID(st, "action", new="action.stash_and_create")
 
             row = layout.row(align=True)
             row.operator("action.push_down", text="Push Down", icon='NLA_PUSHDOWN')