### 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
module.run_command(systemctl, check_rc=True)
        
        found = is_systemd or is_initd
        if is_initd and not is_systemd:
            module.warn('The service (%s) is actually an init script but the system is managed by systemd' % unit)
        
        if module.params['masked'] is not None:
            
            (rc, out, err) = module.run_command("%s is-enabled '%s'" % (systemctl, unit))
            masked = out.strip() == "masked"
            if masked != module.params['masked']:
                result['changed'] = True
                if module.params['masked']:
                    action = 'mask'
                else:
                    action = 'unmask'
                if not module.check_mode:
                    (rc, out, err) = module.run_command("%s %s '%s'" % (systemctl, action, unit))
                    if rc != 0:
                        
                        fail_if_missing(module, found, unit, msg='host')
        
        if module.params['enabled'] is not None:
            if module.params['enabled']:
                action = 'enable'
            else:
                action = 'disable'
            fail_if_missing(module, found, unit, msg='host')
            
            enabled = False