### Summary

The [list of builtin modules](https://docs.ansible.com/ansible/latest/collections/ansible/builtin/index.html) shows two modules with similar names and identical descriptions:

> [systemd module](https://docs.ansible.com/ansible/latest/collections/ansible/builtin/systemd_module.html#ansible-collections-ansible-builtin-systemd-module) – Manage systemd units
> [systemd_service module](https://docs.ansible.com/ansible/latest/collections/ansible/builtin/systemd_service_module.html#ansible-collections-ansible-builtin-systemd-service-module) – Manage systemd units

My guess was that `systemd_service` would manage services running with systemd, and `systemd` would manage `systemd` itself. But the description is identical. The synopsis is identical. The arguments and examples appear identical.

As a user, I expect that if one module has two names, the documentation would state that one is an alias.

Looking at [the code](https://github.com/ansible/ansible/blob/devel/lib/ansible/modules/systemd.py) I see that `systemd` is symlinked to `systemd_service.py`.

Please modify the documentation to state that one is an alias of the other, and they are identical.


### Issue Type

Documentation Report

### Component Name

systemd_service

### Ansible Version

```console
N/A
```


### Configuration

```console
N/A
```


### OS / Environment

N/A

### Additional Information

For context, my objective is to create a service file, and then enable+start it. I was hoping that there would be one module to do that. But then I saw there are two similar ones, and I thought one would create the .service file, and the other would load+run it. But that doesn't appear to be the case either.

### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
requirements:
    - A system managed by systemd.
'''
EXAMPLES = '''
- name: Make sure a service unit is running
  ansible.builtin.systemd_service:
    state: started
    name: httpd
- name: Stop service cron on debian, if running
  ansible.builtin.systemd_service:
    name: cron
    state: stopped
- name: Restart service cron on centos, in all cases, also issue daemon-reload to pick up config changes
  ansible.builtin.systemd_service:
    state: restarted
    daemon_reload: true
    name: crond
- name: Reload service httpd, in all cases
  ansible.builtin.systemd_service:
    name: httpd.service
    state: reloaded
- name: Enable service httpd and ensure it is not masked
  ansible.builtin.systemd_service:
    name: httpd
    enabled: true
    masked: no
- name: Enable a timer unit for dnf-automatic
  ansible.builtin.systemd_service:
    name: dnf-automatic.timer
    state: started