crypto/bio/bio_print.c: improve the precision handling in fmtint

crypto/bio/bio_print.c: improve the precision handling in fmtint

Per [1]:

    * A negative precision is taken as if the precision were omitted.
    * The default precision is 1.
    * For d, i, o, u, x, and X conversion specifiers, if a precision
      is specified, the '0' flag shall be ignored.

[1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/printf.html

Signed-off-by: Eugene Syromiatnikov <esyr@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28177)