Reduce integer-output-format to print-integers-as-characters

Reduce integer-output-format to print-integers-as-characters

The variable now only controls whether characters are printed, not
the radix.  Control chars are printed in human-readable syntax
only when special escapes such as ?\n are available.  Spaces,
formatting and combining chars are excluded (bug#44155).
Done in collaboration with Juri Linkov.

* src/character.c (graphic_base_p):
* src/print.c (named_escape): New functions.
(print_object): Change semantics as described above.
(syms_of_print): Rename integer-output-format.  Update doc string.
* doc/lispref/streams.texi (Output Variables):
* etc/NEWS:
* test/src/print-tests.el (print-integers-as-characters):
Rename and update according to new semantics.  The test now passes.