Some of the enums that indicate operations in the context menu are not
supported for some element types like TSE_SEQUENCE.
From the user's point of view, this looks like a bug since the buttom
is there.
Then populate the enum list dynamically depending on the type.
Also add some calls that were missing from the TSE_SEQUENCE type.
(WM_event_add_notifier and ED_undo_push).
Ref T90637