r/bitwarden_rs: Migrate to podman

Docker is effectively deprecated by Fedora/Red Hat.  It is a pain in the
ass to work with anyway.  Podman integrates better with systemd, and is
in general more aligned with how I prefer to deploy and manage
applications.

I am following the same pattern here that I have used for Home
Assistant, ZWaveJS2MQTT, etc.  The systemd service starts the container
with `podman`, passing the necessary arguments for UID/GID mapping, etc.
Note that, by default, Vaultwarden expects to be able to bind to port
80; since the container is unprivileged, we have to configure it (or
rather, its embedded HTTP server [Rocket](https://rocket.rs)) to listen
on a different port.  We also configure it to listen only on the
loopback, since it is being proxied by Apache to the outside network.

To migrate the data from the Docker volume, we just have to copy the
files and fix their ownership.

The *bitwarden_rs* project was recently renamed to *Vaultwarden*, so I
took this opportunity to update the name in most places within the
*bitwarden_rs* role.

roles/bitwarden_rs/tasks/migration.yml

@@ -0,0 +1,19 @@
+- name: ensure bitwarden_rs docker container is stopped
+  docker_container:
+    name: bitwarden
+    state: absent
+  ignore_errors: true
+- name: ensure bitwarden_rs data directory is moved
+  script: migrate-volume.sh
+  args:
+    creates: /var/lib/vaultwarden/data
+- name: ensure docker service is disabled
+  service:
+    name: docker
+    state: stopped
+    enabled: false
+  ignore_errors: true
+- name: ensure docker is not installed
+  package:
+    name: docker
+    state: absent