Improved argument handling in progress[ing] in src/conditions.lisp

* src/conditions.lisp (progress): allow
  format-control-or-condition-class to be a formatter function; updated
  documentation string accordingly
  (progressing): similar; pass arguments to format string or formatter
  function
* test/macros.lisp (test with-sequence-progress.smoke): test formatter
  functions; for `progressing', check that format string can refer to
  the current sequence element