Replace some CentOS references to support other RHEL derivatives

Not hardcoding 'CentOS' and using the OS family ('RedHat') instead,
we now behave better on Rockylinux and AlmaLinux, etc.

With that said, we may or may not fully support CentOS/Rockylinux/AlmaLinux v8 yet.
Certain things were improved in
https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/300.

v8 support is discussed here: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/300
Certain things (firewalld?) may still be problematic. This patch does not try to address those.
If the remaining issues are confirmed to be fixed in the future, we can mark v8 as supported.

roles/matrix-base/tasks/server_base/setup_redhat8.yml

@@ -0,0 +1,46 @@
+---
+
+- name: Ensure Docker repository is enabled
+  template:
+    src: "{{ role_path }}/files/yum.repos.d/{{ item }}"
+    dest: "/etc/yum.repos.d/{{ item }}"
+    owner: "root"
+    group: "root"
+    mode: 0644
+  with_items:
+    - docker-ce.repo
+  when: matrix_docker_installation_enabled|bool and matrix_docker_package_name == 'docker-ce'
+
+- name: Ensure Docker's RPM key is trusted
+  rpm_key:
+    state: present
+    key: https://download.docker.com/linux/centos/gpg
+  when: matrix_docker_installation_enabled|bool and matrix_docker_package_name == 'docker-ce'
+
+- name: Ensure EPEL is installed
+  yum:
+    name:
+      - epel-release
+    state: latest
+    update_cache: yes
+
+- name: Ensure yum packages are installed
+  yum:
+    name:
+      - "{{ matrix_ntpd_package }}"
+    state: latest
+    update_cache: yes
+
+- name: Ensure Docker is installed
+  yum:
+    name:
+      - "{{ matrix_docker_package_name }}"
+      - python3-pip
+    state: latest
+  when: matrix_docker_installation_enabled|bool
+
+- name: Ensure Docker-Py is installed
+  pip:
+    name: docker-py
+    state: latest
+  when: matrix_docker_installation_enabled|bool