feat: remove hcloud_ prefix from all modules names (#390)

##### SUMMARY

This simplifies the name of the modules from
`hetzner.hcloud.hcloud_firewall` to `hetzner.hcloud.firewall`. While
maintaining backward compatibility with the old names.

Further changes such as updating the test or the documentation will be
done in a future PR to maintain the git history when squashing the PRs.

##### ISSUE TYPE

- Feature Pull Request

.ansible-lint

@@ -5,19 +5,19 @@ exclude_paths:
   - .git/
   - .github/
   - changelogs/
-  - tests/integration/targets/hcloud_certificate
-  - tests/integration/targets/hcloud_firewall
-  - tests/integration/targets/hcloud_floating_ip
-  - tests/integration/targets/hcloud_load_balancer_network
-  - tests/integration/targets/hcloud_load_balancer_service
-  - tests/integration/targets/hcloud_load_balancer_target
-  - tests/integration/targets/hcloud_network
-  - tests/integration/targets/hcloud_placement_group
-  - tests/integration/targets/hcloud_primary_ip
-  - tests/integration/targets/hcloud_route
-  - tests/integration/targets/hcloud_server
-  - tests/integration/targets/hcloud_server_network
-  - tests/integration/targets/hcloud_ssh_key
-  - tests/integration/targets/hcloud_volume
+  - tests/integration/targets/certificate
+  - tests/integration/targets/firewall
+  - tests/integration/targets/floating_ip
+  - tests/integration/targets/load_balancer_network
+  - tests/integration/targets/load_balancer_service
+  - tests/integration/targets/load_balancer_target
+  - tests/integration/targets/network
+  - tests/integration/targets/placement_group
+  - tests/integration/targets/primary_ip
+  - tests/integration/targets/route
+  - tests/integration/targets/server
+  - tests/integration/targets/server_network
+  - tests/integration/targets/ssh_key
+  - tests/integration/targets/volume
   - tests/integration/targets/setup_selfsigned_certificate
   - tests/integration/targets/setup_ssh_keypair