### 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
(rc, out, err) = module.run_command("%s is-enabled '%s' -l" % (systemctl, unit))
            
            if rc == 0:
                enabled = True
                
                if out.splitlines() == ["indirect"] or out.splitlines() == ["alias"]:
                    enabled = False
            elif rc == 1:
                
                if module.params['scope'] == 'system' and \
                        is_initd and \
                        not out.strip().endswith('disabled') and \
                        sysv_is_enabled(unit):
                    enabled = True
            
            result['enabled'] = enabled
            
            if enabled != module.params['enabled']:
                result['changed'] = True
                if not module.check_mode:
                    (rc, out, err) = module.run_command("%s %s '%s'" % (systemctl, action, unit))
                    if rc != 0:
                        module.fail_json(msg="Unable to %s service %s: %s" % (action, unit, out + err))
                result['enabled'] = not enabled
        
        if module.params['state'] is not None:
            fail_if_missing(module, found, unit, msg="host")
            
            result['state'] = module.params['state']