api: generate v3alpha from v2 via protoxform. (#8356)

This takes protoxform from being a v2 format tool to being able to
generate something similar to what ./api/migration/v3alpha.sh generates.

Risk level: Low (v3alpha not used yet)
Testing: fix_format, manual verification that the delta from
  ./api/migration/v3alpha.sh makes sense (for now).

Signed-off-by: Harvey Tuch <htuch@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 89539d31e9fe749418d499352897c7acb474fab2

envoy/api/v3alpha/cluster/circuit_breaker.proto

@@ -5,8 +5,6 @@ package envoy.api.v3alpha.cluster;
 option java_outer_classname = "CircuitBreakerProto";
 option java_multiple_files = true;
 option java_package = "io.envoyproxy.envoy.api.v3alpha.cluster";
-option csharp_namespace = "Envoy.Api.V2.ClusterNS";
-option ruby_package = "Envoy.Api.V2.ClusterNS";
 
 import "envoy/api/v3alpha/core/base.proto";
 

envoy/api/v3alpha/cluster/filter.proto

@@ -5,8 +5,6 @@ package envoy.api.v3alpha.cluster;
 option java_outer_classname = "FilterProto";
 option java_multiple_files = true;
 option java_package = "io.envoyproxy.envoy.api.v3alpha.cluster";
-option csharp_namespace = "Envoy.Api.V2.ClusterNS";
-option ruby_package = "Envoy.Api.V2.ClusterNS";
 
 import "google/protobuf/any.proto";
 

envoy/api/v3alpha/cluster/outlier_detection.proto

@@ -5,8 +5,6 @@ package envoy.api.v3alpha.cluster;
 option java_outer_classname = "OutlierDetectionProto";
 option java_multiple_files = true;
 option java_package = "io.envoyproxy.envoy.api.v3alpha.cluster";
-option csharp_namespace = "Envoy.Api.V2.ClusterNS";
-option ruby_package = "Envoy.Api.V2.ClusterNS";
 
 import "google/protobuf/duration.proto";
 import "google/protobuf/wrappers.proto";

envoy/api/v3alpha/listener/listener.proto

@@ -5,8 +5,6 @@ package envoy.api.v3alpha.listener;
 option java_outer_classname = "ListenerProto";
 option java_multiple_files = true;
 option java_package = "io.envoyproxy.envoy.api.v3alpha.listener";
-option csharp_namespace = "Envoy.Api.V2.ListenerNS";
-option ruby_package = "Envoy.Api.V2.ListenerNS";
 
 import "envoy/api/v3alpha/auth/cert.proto";
 import "envoy/api/v3alpha/core/address.proto";

envoy/api/v3alpha/listener/quic_config.proto

@@ -5,8 +5,6 @@ package envoy.api.v3alpha.listener;
 option java_outer_classname = "QuicConfigProto";
 option java_multiple_files = true;
 option java_package = "io.envoyproxy.envoy.api.v3alpha.listener";
-option csharp_namespace = "Envoy.Api.V2.ListenerNS";
-option ruby_package = "Envoy.Api.V2.ListenerNS";
 
 import "google/protobuf/duration.proto";
 import "google/protobuf/wrappers.proto";

envoy/api/v3alpha/listener/udp_listener_config.proto

@@ -5,8 +5,6 @@ package envoy.api.v3alpha.listener;
 option java_outer_classname = "UdpListenerConfigProto";
 option java_multiple_files = true;
 option java_package = "io.envoyproxy.envoy.api.v3alpha.listener";
-option csharp_namespace = "Envoy.Api.V2.ListenerNS";
-option ruby_package = "Envoy.Api.V2.ListenerNS";
 
 import "google/protobuf/any.proto";
 import "google/protobuf/struct.proto";

envoy/config/trace/v3alpha/trace.proto

@@ -179,7 +179,7 @@ message OpenCensusConfig {
   // also be set.
   bool zipkin_exporter_enabled = 5;
 
-  // The URL to Zipkin, e.g. "http://127.0.0.1:9411/api/v3alpha/spans"
+  // The URL to Zipkin, e.g. "http://127.0.0.1:9411/api/v2/spans"
   string zipkin_url = 6;
 
   // Enables the OpenCensus Agent exporter if set to true. The address must also