feat: support per-component Deployment labels and annotations

[somaz94]

What

Adds top-level deploymentLabels and deploymentAnnotations values, keyed per component (keda / metricsAdapter / webhooks), and wires them into the metadata.labels / metadata.annotations of the operator, metrics-apiserver and webhooks Deployments.

Why

Today the only way to set Deployment-level labels/annotations is additionalLabels / additionalAnnotations, which are shared across every component. There is no way to give a different value per component. The use case in #418 is Datadog unified service tagging, where each Deployment needs a distinct service (operator / metrics-apiserver / webhook).

This mirrors the existing per-component podLabels / podAnnotations interface exactly, so the shape is already familiar:

deploymentAnnotations:
  keda:
    ad.datadoghq.com/tags: '{"service":"operator"}'
  metricsAdapter:
    ad.datadoghq.com/tags: '{"service":"metrics-apiserver"}'
  webhooks:
    ad.datadoghq.com/tags: '{"service":"webhook"}'
deploymentLabels:
  keda:
    team: platform

When set alongside additionalAnnotations, both are merged onto the Deployment.

A note on the approach

In #418 you raised the question of whether to follow the existing podLabels/podAnnotations map style or move toward a {component}.foo.bar nested style. I went with the existing top-level map style here for consistency with podLabels/podAnnotations and to keep the diff small. Happy to refactor to the per-component nested style if that is the direction you prefer.

Validation (local)

• helm lint keda passes.
• Default render is byte-identical to main (new keys default to {}, so existing installs see no change).
• helm template with the values above merges additionalAnnotations + per-component deploymentAnnotations, and appends per-component deploymentLabels, on all three Deployments.
• Installed on a kind v1.34 cluster: all three Deployments carry the expected per-component metadata.labels / metadata.annotations on the live specs, and all pods reach Running.
• keda/Chart.yaml version intentionally not bumped, per CONTRIBUTING (chart versions are released with KEDA core).

Resolves #418