Enhance k3s_agent role with idiomatic Ansible practices for better maintainability.

**Added:**

- Structured HTTP Proxy Configuration Block - Added a structured block in
  `http_proxy.yml` for managing HTTP proxy settings, aligning with Ansible's
  recommended practices. This includes creating directories and deploying
  configuration files in a clear, modular fashion.
- Conditional Execution for Proxy Setup - Implemented conditional execution
  for the proxy setup in `http_proxy.yml`, utilizing `proxy_env` to adhere
  to Ansible's best practices for conditional tasks.
- Improved PXE-Boot System Check Block - Introduced a more structured approach
  in `main.yml` for checking PXE-booted systems, enhancing readability and
  maintainability.

**Changed:**

- Adopted Ansible Builtin Modules - Transitioned existing tasks to use
  `ansible.builtin` modules, ensuring compatibility and future-proofing the
  role.
- Refined Task Grouping - Reorganized tasks into logical blocks, improving
  the overall structure and readability, and showcasing Ansible's capabilities
  for efficient task management.
- Updated K3s Service Configuration - Modified the K3s service configuration
  task in `main.yml` for a more streamlined approach using Ansible's template
  module, reflecting community-driven best practices.

**Removed:**

- Streamlined Task Definitions - Optimized task definitions to reduce
  redundancy, focusing on clarity and adherence to the evolving Ansible
  community standards.

roles/k3s_agent/tasks/http_proxy.yml

@@ -1,18 +1,19 @@
 ---
+- name: Manage K3s HTTP Proxy Configuration
+  when: proxy_env is defined
+  block:
+    - name: Create k3s.service.d directory
+      ansible.builtin.file:
+        path: '{{ systemd_dir }}/k3s.service.d'
+        owner: root
+        group: root
+        state: directory
+        mode: '0755'
 
-- name: Create k3s.service.d directory
-  file:
-    path: '{{ systemd_dir }}/k3s.service.d'
-    state: directory
-    owner: root
-    group: root
-    mode: '0755'
-
-
-- name: Copy K3s http_proxy conf file
-  template:
-    src: "http_proxy.conf.j2"
-    dest: "{{ systemd_dir }}/k3s.service.d/http_proxy.conf"
-    owner: root
-    group: root
-    mode: '0755'
+    - name: Deploy the K3s http_proxy configuration file
+      ansible.builtin.template:
+        src: "http_proxy.conf.j2"
+        dest: "{{ systemd_dir }}/k3s.service.d/http_proxy.conf"
+        owner: root
+        group: root
+        mode: '0755'