bump up container image versions and drop using CPack

We have already provided DEB packages in launchpad PPA and RPM packages
in COPR. Thus, we need no more deb/rpm packages in Github releases. The
single binary build of mscp is an execptio.

Updated container image versions:
- almalinux	8.8  -> 9.3
- rocky		8.8  -> 8.9, and 9.3 is added
- alpine	3.17 -> 3.19

Dockerfile/ubuntu-20.04.Dockerfile

@@ -0,0 +1,35 @@
+FROM ubuntu:20.04
+
+ARG DEBIAN_FRONTEND=noninteractive
+RUN set -ex && apt-get update && apt-get install -y --no-install-recommends \
+	ca-certificates
+
+# install pytest, and sshd for test
+RUN apt-get install -y --no-install-recommends  \
+        python3 python3-pip python3-dev openssh-server
+
+RUN python3 -m pip install pytest
+
+
+# preparation for sshd
+RUN  mkdir /var/run/sshd        \
+        && ssh-keygen -f /root/.ssh/id_rsa -N ""                \
+        && mv /root/.ssh/id_rsa.pub /root/.ssh/authorized_keys
+
+
+ARG mscpdir="/mscp"
+
+COPY . ${mscpdir}
+
+# install build dependency
+RUN ${mscpdir}/scripts/install-build-deps.sh
+
+
+# build
+RUN cd ${mscpdir}			\
+	&& rm -rf build			\
+	&& cmake -B build		\
+	&& cd ${mscpdir}/build		\
+	&& make	-j 2			\
+	&& make install
+