Promote ServiceTrafficDistribution feature-gate to beta and enable by default. Also add missing integration tests.

[gauravkghildiyal]

What type of PR is this?

/kind feature

What this PR does / why we need it:

• Promote ServiceTrafficDistribution feature-gate to beta and enable by default.
• Add more test coverage for feature enablement and disablement.

Does this PR introduce a user-facing change?

The Service trafficDistribution field has graduated to beta and is now available for configuration by default, without the need to enable any feature flag. Services that do not have the field configured will continue to operate with their existing behavior. Refer to the documentation https://kubernetes.io/docs/concepts/services-networking/service/#traffic-distribution for more details.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

- [KEP]: https://github.com/kubernetes/enhancements/tree/master/keps/sig-network/4444-service-traffic-distribution

/sig network
/priority important-soon

/assign @thockin
/assign @robscott

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[aojea]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 6d704b13e085099df999ddcf0524ee63a2586eb4

[thockin]

Thanks!

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gauravkghildiyal, thockin

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