Stop truncating strings too much in cl-print-string-with-limit

Stop truncating strings too much in cl-print-string-with-limit

This fixes bug#65680, by introducing a new variable limiting
the length of a printed string, rather than abusing
print-length for that purpose.

* lisp/emacs-lisp/cl-print.el (cl-print-string-length): New
variable.
(cl-print-object <string>, cl-print--string-props): Use
cl-print-string-length rather than print-length here.
(cl-print-string-with-limit): bind cl-print-string-length based
on argument `limit'.  Decrement it by a quarter at each trial
iteration of printing.