### 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.warn('daemon-reload failed, but target is a chroot or systemd is offline. Continuing. Error was: %d / %s' % (rc, err))
            else:
                module.fail_json(msg='failure %d during daemon-reload: %s' % (rc, err))
    
    if module.params['daemon_reexec'] and not module.check_mode:
        (rc, out, err) = module.run_command("%s daemon-reexec" % (systemctl))
        if rc != 0:
            if is_chroot(module) or os.environ.get('SYSTEMD_OFFLINE') == '1':
                module.warn('daemon-reexec failed, but target is a chroot or systemd is offline. Continuing. Error was: %d / %s' % (rc, err))
            else:
                module.fail_json(msg='failure %d during daemon-reexec: %s' % (rc, err))
    if unit:
        found = False
        is_initd = sysv_exists(unit)
        is_systemd = False
        
        (rc, out, err) = module.run_command("%s show '%s'" % (systemctl, unit))
        if rc == 0 and not (request_was_ignored(out) or request_was_ignored(err)):
            
            if out:
                result['status'] = parse_systemctl_show(to_native(out).split('\n'))
                is_systemd = 'LoadState' in result['status'] and result['status']['LoadState'] != 'not-found'
                is_masked = 'LoadState' in result['status'] and result['status']['LoadState'] == 'masked'
                
                if is_systemd and not is_masked and 'LoadError' in result['status']:
                    module.fail_json(msg="Error loading unit file '%s': %s" % (unit, result['status']['LoadError']))
        
        elif err and rc == 1 and 'Failed to parse bus message' in err:
            result['status'] = parse_systemctl_show(to_native(out).split('\n'))
            unit_base, sep, suffix = unit.partition('@')