feat(xds): rework DeltaXds to use metadata instead of proto

[lukidzi]

Motivation

We shouldn't change the proto schema but instead use metadata.

Implementation information

• Remove proto file and field from Dataplane/ZoneIngress/ZoneEgress. It should be safe since clients (mink) were not able to set this property and only global knew about it
• Introduce a new variable for kuma-dp KUMA_DATAPLANE_RUNTIME_ENVOY_XDS_TRANSPORT_PROTOCOL_VARIANT which allow setting specific variant of the xds protocol
• Keep kuma.io/xds-transport-protocol-variant in the k8s to simplify delta testing for the user

Supporting documentation

Fix #13461

[github-actions]

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[Icarus9913]

@lukidzi Please double check pkg/plugins/runtime/k8s/controllers/pod_converter.go PodConverter struct DeltaXds property, it seems not used anymore

[lobkovilya]

should we call this one SOTW_GRPC?

[lukidzi]

Envoy configuration reference to SOTW as GRPC so I wanted to keep them the same

[lobkovilya]

why do we need UseDeltaXds if you can always call params.Features.HasFeature(xds_types.FeatureDeltaGRPC)

[lukidzi]

We need since you can always enable it on the control-plane level and later you need to set it

[Icarus9913]

LGTM