### Brief description of Pull Request

Release the Alloy Helm chart 1.10.0: bump `appVersion` to Alloy v1.17.0
and ship the new `service.externalTrafficPolicy` support from the
externalTrafficPolicy PR (#4511).

### Pull Request Details

That externalTrafficPolicy PR merged from a stale branch and deleted the
`1.9.0 (2026-06-08)` CHANGELOG header, which left 1.9.0's
already-shipped entries (externalHPA, the v1.16.3 bump, the configmap
key fix) sitting back under _Unreleased_. This restores that header and
pulls only the externalTrafficPolicy entry up under the new `1.10.0`
section. The rest is the standard release bump — Chart.yaml, helm-docs
README badges, and regenerated golden test snapshots (`v1.16.3 →
v1.17.0`).

### PR Checklist

- [x] Documentation added
- [x] Tests updated