First of all, let's init with the main procedure label (stripped of
leading/traling spaces, of mnemonic underscore and of ellipsis) as
progress status for gimp_progress_init().
Then reuse this main label for all subsequent progress updates by the
same top procedure.
Finally "pulse" the progress at each update to make it more like
progression actually happens.
This is a first experiment to see if not having progress API in
Script-Fu is fine (#12948), by having better progression defaults.
Fix unreported issue that new-style dialog using GimpProcedureDialog
does not display progress.
Change progress reporting to use app's status bar, for all scripts,
old and new style.
As before, report progress whenever a script calls a PDB procedure,
by putting the procedure name in the status bar.
Eliminate progress bar widget from old-style script dialog.
Since it was failing on Wayland, and since it is inconsitent
with new style dialog using GimpProcedureDialog.
