r/blackbox-exporter: Rework to run as container

Instead of downloading the `blackbox_exporter` binary from GitHub and
copying it to the managed node, the _blackbox-exporter_ role now
installs _podman_ and configures a systemd container unit (Quadlet) to
run it in a container.  This simplifies the deployment considerably, and
will make updating easier (just run the playbook with `-e
blackbox_exporter_pull_image=true`).

roles/blackbox-exporter/handlers/main.yml

@@ -2,12 +2,12 @@
   systemd:
     daemon_reload: true
 
-- name: restart blackbox_exporter
+- name: restart blackbox-exporter
   service:
-    name: blackbox_exporter
+    name: blackbox-exporter
     state: restarted
 
-- name: reload blackbox_exporter
+- name: reload blackbox-exporter
   service:
-    name: blackbox_exporter
+    name: blackbox-exporter
     state: reloaded