Backport v2021 <- v2022dev2: Switch to OpenSSL

Backport !49 (merged) to follow the Apertis guidelines, which chooses OpenSSL as TLS stack, switch systemd to be build against it.

In the same line drop systemd-journal-remote and its dependency libmicrohttpd-dev since it can only be built against GnuTLS but has no value for Apertis.

Signed-off-by: Walter Lozano walter.lozano@collabora.com