### Summary

When running `ansible -m setup host`, reported `ansible_memtotal_mb` fact changes between invocations.
That's because `setup` reads available non-kernel memory, which fluctuates:

https://github.com/ansible/ansible/blob/2797dc644aa8c809444ccac64cad63e0d9a3f9fe/lib/ansible/module_utils/facts/hardware/openbsd.py#L96-L97

To read total available memory, `hw.physmem` key should be used. Refer to the https://man.openbsd.org/sysctl.2 man, `HW_USERMEM` and `HW_PHYSMEM`.

### Issue Type

Bug Report

### Component Name

setup

### Ansible Version

```console
All.

https://github.com/ansible/ansible/blob/devel/lib/ansible/module_utils/facts/hardware/openbsd.py#L97
```


### Configuration

```console
N/A
```


### OS / Environment

OpenBSD 7.0

### Steps to Reproduce

On OpenBSD host, run this few times:

```
ansible -m setup openbsd_host | grep memtotal
```

Total memory value will be fluctuation between calls.

### Expected Results

I expect to see total installed memory.

### Actual Results

```console
N/A
```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
memory_facts = {}
        
        
        
        
        rc, out, err = self.module.run_command("/usr/bin/vmstat")
        if rc == 0:
            memory_facts['memfree_mb'] = int(out.splitlines()[-1].split()[4]) // 1024
            memory_facts['memtotal_mb'] = int(self.sysctl['hw.usermem']) // 1024 // 1024
        
        
        
        
        rc, out, err = self.module.run_command("/sbin/swapctl -sk")
        if rc == 0:
            swaptrans = {ord(u'k'): None,
                         ord(u'm'): None,
                         ord(u'g'): None}
            data = to_text(out, errors='surrogate_or_strict').split()
            memory_facts['swapfree_mb'] = int(data[-2].translate(swaptrans)) // 1024
            memory_facts['swaptotal_mb'] = int(data[1].translate(swaptrans)) // 1024
        return memory_facts
    def get_uptime_facts(self):