feat(xds): rework DeltaXds to use metadata instead of proto (#13467)

## 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

---------

Signed-off-by: Lukasz Dziedziak <[email protected]>

Author: lukidzi

api/mesh/v1alpha1/dataplane.pb.go

@@ -7,7 +7,6 @@ option go_package = "github.com/kumahq/kuma/api/mesh/v1alpha1";
 import "api/mesh/options.proto";
 import "api/mesh/v1alpha1/metrics.proto";
 import "api/mesh/v1alpha1/envoy_admin.proto";
-import "api/mesh/v1alpha1/envoy.proto";
 import "google/protobuf/duration.proto";
 import "google/protobuf/wrappers.proto";
 import "validate/validate.proto";
@@ -372,7 +371,4 @@ message Dataplane {
   // Deprecated: this feature will be removed for Universal; on Kubernetes, it's
   // not needed anymore.
   Probes probes = 3;
-
-  // EnvoyConfiguration provides additional configuration for the Envoy sidecar.
-  EnvoyConfiguration envoy = 4;
 }

api/mesh/v1alpha1/dataplane.proto

@@ -1,16 +1,4 @@
 properties:
-  envoy:
-    description: EnvoyConfiguration provides additional configuration for the Envoy
-      sidecar.
-    properties:
-      xdsTransportProtocolVariant:
-        description: |-
-          xDSTransportProtocol provides information about protocol used for
-          configuration exchange between control-plane and Envoy sidecar.
-        oneOf:
-        - type: string
-        - type: integer
-    type: object
   labels:
     additionalProperties:
       type: string

api/mesh/v1alpha1/dataplane/schema.yaml

@@ -4,18 +4,6 @@ components:
       properties:
         dataplane:
           properties:
-            envoy:
-              description: EnvoyConfiguration provides additional configuration for
-                the Envoy sidecar.
-              properties:
-                xdsTransportProtocolVariant:
-                  description: |-
-                    xDSTransportProtocol provides information about protocol used for
-                    configuration exchange between control-plane and Envoy sidecar.
-                  oneOf:
-                  - type: string
-                  - type: integer
-              type: object
             metrics:
               description: |-
                 Configuration for metrics that should be collected and exposed by the