Convered GPGKey tests to use Factory and APIs for dependent entities

- Using make_gpgkey for create/update/delete tests
- Used api's mostly for tests where we are associating GPGKey with product/repo etc.

To be more readable, I think is better to separate `orm.StringField(str_type=('alphanumeric',).get_value()` in its own line like:

```python
org_name = orm.StringField(str_type=('alphanumeric',).get_value()
org_attrs = entities.Organization(name=org_name).create()
```