Fix #6724: Allow setting enableServiceLinks on the Integration pod template

[lsergio]

Motivation

Fixes #6724

Users need to control the Kubernetes pod-level enableServiceLinks flag on an
Integration. When many Services exist in a namespace, Kubernetes injects a
{SVC}_SERVICE_HOST / {SVC}_SERVICE_PORT env var per Service into every
container (the Docker-links compatibility feature). This bloats the environment
and can slow pod startup, so operators commonly want to set
enableServiceLinks: false. There was previously no way to express this on an
Integration.

What this does

Adds an EnableServiceLinks *bool field to the curated v1.PodSpec used by
spec.template.spec, mirroring the upstream Kubernetes PodSpec field
(json enableServiceLinks, defaults to true).

apiVersion: camel.apache.org/v1
kind: Integration
spec:
  template:
    spec:
      enableServiceLinks: false

The pod trait marshals spec.template.spec and applies it as a
strategic merge patch onto the workload pod spec, so the new field
propagates to Deployment, CronJob and Knative Service pods with no additional
trait logic.

Generated artifacts

Regenerated and committed:

• CRDs: camel.apache.org_integrations.yaml, camel.apache.org_pipes.yaml
• Helm CRD bundle: helm/camel-k/crds/camel-k-crds.yaml
• zz_generated.deepcopy.go
• apply-configuration client podspec.go

Note on deprecation

PodSpecTemplate / v1.PodSpec and the pod trait are marked
Deprecated: to be removed in future versions ("use container, init-containers
or owner traits instead"). I placed the field here because enableServiceLinks
is a pod-level toggle that no current non-deprecated trait can set — the
pod template is genuinely the only mechanism available today. Happy to move it
to a different home (e.g. a dedicated trait) if the maintainers prefer that over
extending the deprecated surface.

Testing

• New unit test TestEnableServiceLinks in pkg/trait/pod_test.go verifies
  enableServiceLinks: false propagates to the deployment pod spec.
• go build, go vet, gofmt, and golangci-lint (v2.12.2) pass on the
  affected packages; full pkg/trait suite is green.

Suggested reviewers

• @squakez (Pasquale Congiusti) — most active on the pod trait / API and author
  of the Pod-trait deprecation; best placed to weigh in on the deprecation note.
• Pranjul Kalsi — recent contributor to this area.

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This change was prepared by Claude Code on behalf of Luis Sergio Carneiro (@lsergio).