Force newline when not present in query format

[tomwhite]

The idea is to append a \n if there isn't one in the format string.

% vcztools query -f '%AC' vcz_test_cache/sample.vcf.vcz
......1,1..
% bcftools query -f '%AC' tests/data/vcf/sample.vcf.gz
.
.
.
.
.
.
1,1
.
.

This was introduced in bcftools 1.18; there's some discussion at samtools/bcftools#1969

We should add the -N, --disable-automatic-newline flag at the same time so users can suppress this behaviour if desired.