Get rid of the custom `paginated()` and use the built-in `iterator()`

The custom `BaseQuerySet.paginated()` performs extremely poorly in terms of compute time and memory usage compared to the built-in `iterator()`.

## Below is an example where we compare `.paginated()` with `.iterator()` for iterating over 8 million advisory data.

### Using custom `paginated()`

Even after 20 minutes, the iteration is not completed, and the ETA keeps getting worse and worse.

```python
Iterating advisory data using custom BaseQuerySet.paginated()
INFO 2025-03-07 08:56:41.500 Pipeline [IterateAdvisory] starting
INFO 2025-03-07 08:56:41.500 Step [iterate_advisories] starting
INFO 2025-03-07 08:56:41.796 Iterating over 8073782 Advisory objects.
INFO 2025-03-07 08:57:50.106 Progress: 10% (807379/8073782) ETA: 615 seconds (10.2 minutes)
INFO 2025-03-07 09:00:09.226 Progress: 20% (1614757/8073782) ETA: 830 seconds (13.8 minutes)
INFO 2025-03-07 09:03:34.920 Progress: 30% (2422135/8073782) ETA: 964 seconds (16.1 minutes)
INFO 2025-03-07 09:09:04.444 Progress: 40% (3229513/8073782) ETA: 1114 seconds (18.6 minutes)
INFO 2025-03-07 09:16:32.571 Progress: 50% (4036891/8073782) ETA: 1191 seconds (19.9 minutes)
^CCommandError: Keyboard interrupt received. Stopping...
```

### Using built-in `iterator()`

It takes around 4 minutes to iterate over 8 million advisories.
```python
Iterating advisory data using built-in .iterator()
INFO 2025-03-07 10:02:43.483 Pipeline [IterateAdvisory] starting
INFO 2025-03-07 10:02:43.483 Step [iterate_advisories] starting
INFO 2025-03-07 10:02:44.042 Iterating over 8073782 Advisory objects.
INFO 2025-03-07 10:05:00.181 Progress: 10% (807379/8073782) ETA: 1225 seconds (20.4 minutes)
INFO 2025-03-07 10:05:19.790 Progress: 20% (1614757/8073782) ETA: 623 seconds (10.4 minutes)
INFO 2025-03-07 10:05:37.013 Progress: 30% (2422135/8073782) ETA: 404 seconds (6.7 minutes)
INFO 2025-03-07 10:05:50.865 Progress: 40% (3229513/8073782) ETA: 280 seconds (4.7 minutes)
INFO 2025-03-07 10:06:01.161 Progress: 50% (4036891/8073782) ETA: 197 seconds (3.3 minutes)
INFO 2025-03-07 10:06:11.465 Progress: 60% (4844270/8073782) ETA: 138 seconds (2.3 minutes)
INFO 2025-03-07 10:06:21.761 Progress: 70% (5651648/8073782) ETA: 93 seconds (1.6 minutes)
INFO 2025-03-07 10:06:32.129 Progress: 80% (6459026/8073782) ETA: 57 seconds
INFO 2025-03-07 10:06:42.248 Progress: 90% (7266404/8073782) ETA: 26 seconds
INFO 2025-03-07 10:06:52.325 Progress: 100% (8073782/8073782)
INFO 2025-03-07 10:06:52.587 Step [iterate_advisories] completed in 249 seconds (4.2 minutes)
INFO 2025-03-07 10:06:52.587 Pipeline completed in 249 seconds (4.2 minutes)
```