feat(Dockerfile): Install the rng-tools5 package

This adds a bridge to hardware TRNGs to increase bandwith and entropy of
the `/dev/random` device. This is a better solution than [1], which will
get reverted in a following change.

[1]: #9856

Signed-off-by: Sebastian Schuberth <sebastian@doubleopen.org>

Author: sschuberth

Dockerfile

@@ -60,6 +60,7 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
     openssh-client \
     openssl \
     procps \
+    rng-tools5 \
     rsync \
     sudo \
     tzdata \