[Console] Improved xml generated when listing commands

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

I marked this PR as BC, as it break the xml schema generated by the command __app/console list --xml__

It replaces the first node (currently _<symfony>_) by a more generic node name and adds the application name and application version if specified in the Application constructor.

Before (using composer console that uses symfony console component):
```
<?xml version="1.0" encoding="UTF-8"?>
<symfony>
    ...
</symfony>
```

After (using composer console that uses symfony console component)
```
<?xml version="1.0" encoding="UTF-8"?>
<application name="Composer" version="x.x.x">
    ...
</application>
```