### 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
enabled: true
- name: Just force systemd to reread configs (2.4 and above)
  ansible.builtin.systemd_service:
    daemon_reload: true
- name: Just force systemd to re-execute itself (2.8 and above)
  ansible.builtin.systemd_service:
    daemon_reexec: true
- name: Run a user service when XDG_RUNTIME_DIR is not set on remote login
  ansible.builtin.systemd_service:
    name: myservice
    state: started
    scope: user
  environment:
    XDG_RUNTIME_DIR: "/run/user/{{ myuid }}"
'''
RETURN = '''
status:
    description: A dictionary with the key=value pairs returned from C(systemctl show).
    returned: success
    type: dict
    sample: {
            "ActiveEnterTimestamp": "Sun 2016-05-15 18:28:49 EDT",
            "ActiveEnterTimestampMonotonic": "8135942",
            "ActiveExitTimestampMonotonic": "0",
            "ActiveState": "active",
            "After": "auditd.service systemd-user-sessions.service time-sync.target systemd-journald.socket basic.target system.slice",
            "AllowIsolate": "no",
            "Before": "shutdown.target multi-user.target",
            "BlockIOAccounting": "no",
            "BlockIOWeight": "1000",