Keep journal files compatible with older versions

Keep journal files compatible with older versions

Disable the KEYED-HASH journal feature by default and keep LZ4 (instead
of ZSTD) as default compression for new journal files. Otherwise journal
files are incompatible and can't be read by older journalctl
implementations.

This patch can be dropped in bullseye+1, as journalctl from bullseye
will then be able to read journal files with those features.

Closes: #968055
Gbp-Pq: Topic debian
Gbp-Pq: Name Keep-journal-files-compatible-with-older-versions.patch