Provide a way to fetch lists of all vulnerable CPEs and PURLs

Add extra actions on the `packages` and `cpes` API endpoint that would return a single list of all vulnerable PURLs and CPEs.

For examples:

```
GET /api/packages/all/

[
"purl1",
"purl2",
"purl3",
...
]
```

```
GET /api/cpes/all/

[
"cpe1",
"cpe2",
"cpe3",
...
]
```

Make sure to not include PURLs nor CPEs that are not vulnerable.