Annotations enabling a feature can't affect dependency resolution

AFAICT if you do something like:

```
annotations = {
"rustls": [
crate.annotation(
crate_features = ["fips"],
),
],
```

This doesn't impact the dependencies resolved. Splicing appears to completely ignore annotations, and we only apply them at generation time, which is too late to impact resolution.

We should grab feature annotations at splice time so they impact dependency resolution.