Use table helper to render DebugCommand output

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT


Before:
```
Name                     Transport Spool Delivery Single Address
bulk                     smtp      YES   YES                    
default (default mailer) smtp      NO    YES 
```

After:
```
+--------------------------+-----------+-------+----------+----------------+
| Name                     | Transport | Spool | Delivery | Single Address |
+--------------------------+-----------+-------+----------+----------------+
| bulk                     | smtp      | YES   | YES      |                |
| default (default mailer) | smtp      | NO    | YES      |                |
+--------------------------+-----------+-------+----------+----------------+
```
This looks wrong to me. When you display a single mailer, it makes no sense to use the table layout