Optimise Aethel search code

The search logic in `AethelQueryView.get()` works but is not fully optimized. Instead of doing this (in lines 106ff.)

```python
# Check whether we have already added this sample for this result
existing_sample = next(
(s for s in result.samples if s.name == sample.name),
None,
)
```
it is worth investigating if we can keep track of the sample earlier in the `for` loop.