Move extrapackage installation into separate role and make it more flexible

- Introduce `extra_pkgs1` - `extra_pkgs10`
- Introduce `extra_pkgs_bpo1` - `extra_pkgs_bpo10`
- Move package-list from lmn_teacherlaptop into inventory as extra_pkgs1

roles/lmn_extrapkgs/defaults/main.yml

@@ -0,0 +1,2 @@
+extra_pkgs: []
+extra_pkgs_bpo: []

roles/lmn_extrapkgs/tasks/main.yaml

@@ -0,0 +1,27 @@
+---
+- name: Merge extra_pkgs and extra_pkgs_bpo lists
+  ansible.builtin.set_fact:
+    extra_pkgs: "{{ extra_pkgs + lookup('vars', 'extra_pkgs' + item, default=[]) }}"
+    extra_pkgs_bpo: "{{ extra_pkgs_bpo + lookup('vars', 'extra_pkgs_bpo' + item, default=[]) }}"
+  loop: "{{ range(1, 11) | map('string') | list }}"
+
+- name: Install extra packages from stable
+  ansible.builtin.apt:
+    name: "{{ extra_pkgs }}"
+  when: extra_pkgs|length
+
+- name: Add backports for {{ ansible_distribution_release }}
+  ansible.builtin.apt_repository:
+    repo: >
+      deb http://deb.debian.org/debian/ {{ ansible_distribution_release }}-backports
+      main non-free-firmware
+    state: present
+    update_cache: true
+  when: extra_pkgs_bpo|length
+
+- name: Install extra packages from backports
+  ansible.builtin.apt:
+    name: "{{ extra_pkgs_bpo }}"
+    state: latest # noqa package-latest
+    default_release: "{{ ansible_distribution_release }}-backports"
+  when: extra_pkgs_bpo|length