thrift_proxy: move protobuf to api/config hierarchy (#3963)

As discussed in Slack, these should have been under api/config/filter/network
to begin with. Added a note to the style doc to make this clear in the
future.

*Risk level*: low (rename only)
*Testing*: existing tests suffice
*Doc Changes*: n/a
*Release Notes*: updated

Signed-off-by: Stephan Zuercher <stephan@turbinelabs.io>

Mirrored from https://github.com/envoyproxy/envoy @ 1dfde38343e7dfafe2c9f211229109bb22491257

STYLE.md

@@ -131,3 +131,6 @@ the build system to prevent circular dependency formation. Package group
 `//envoy/api/v2:friends` selects consumers of the core API package (services and configs)
 and is the default visibility for the core API packages. The default visibility
 for services and configs should be `//docs` (proto documentation tool).
+
+Extensions should use the regular hierarchy. For example, configuration for network filters belongs
+in a package under `envoy.config.filter.network`.

envoy/config/filter/network/thrift_proxy/v2alpha1/route.proto

@@ -1,6 +1,6 @@
 syntax = "proto3";
 
-package envoy.extensions.filters.network.thrift_proxy.v2alpha1;
+package envoy.config.filter.network.thrift_proxy.v2alpha1;
 option go_package = "v2";
 
 import "validate/validate.proto";

envoy/config/filter/network/thrift_proxy/v2alpha1/router/router.proto

@@ -1,6 +1,6 @@
 syntax = "proto3";
 
-package envoy.extensions.filters.network.thrift_proxy.v2alpha1.router;
+package envoy.config.filter.network.thrift_proxy.v2alpha1.router;
 option go_package = "router";
 
 // [#protodoc-title: Thrift Router]

envoy/config/filter/network/thrift_proxy/v2alpha1/thrift_proxy.proto

@@ -1,9 +1,9 @@
 syntax = "proto3";
 
-package envoy.extensions.filters.network.thrift_proxy.v2alpha1;
+package envoy.config.filter.network.thrift_proxy.v2alpha1;
 option go_package = "v2";
 
-import "envoy/extensions/filters/network/thrift_proxy/v2alpha1/route.proto";
+import "envoy/config/filter/network/thrift_proxy/v2alpha1/route.proto";
 
 import "validate/validate.proto";
 import "gogoproto/gogo.proto";