To be more consistent with `ViewableData`, whose `setField()` method will fallback on [assigning properties arbitrarily](https://github.com/silverstripe/silverstripe-framework/blob/4/src/View/ViewableData.php#L213), `DBComposite` shouldn't bail out of `setField` when the field specified isn't in the record.
Arbitrary property assignment is particularly important in injection.
```yaml
SilverStripe\ORM\FieldType\DBComposite:
dependencies:
myService: %$Service
```
Right now, that fails, because `$obj->myService = Service` invokes `__set()` which calls `setField()` which refuses the assignment when `myService`is not in the record.
