Avoid extra output in Vprin1_to_string_buffer (bug#78842)

Avoid extra output in Vprin1_to_string_buffer (bug#78842)

print_error_message can throw after producing some output, so use
unwind-protect to ensure prin1-to-string-buffer is cleared.

* src/print.c (erase_prin1_to_string_buffer): New.
(Ferror_message_string): Use it to catch errors thrown in
'print_error_message'.
* test/src/print-tests.el (error-message-string-circular): Expand
test.

(cherry picked from commit 6b19eb53c5048cfec1f3601afb44f94ebbb9d138)