Fix std schema package names, remove json-test.capnp

This commit fixes the package names generated by `gen.sh import`,
and removes `json-test.capnp` as it is unnecessary.

std/capnp/compat/byte-stream.capnp

@@ -45,4 +45,4 @@ interface ByteStream {
 }
 using Go = import "/go.capnp";
 $Go.package("bytestream");
-$Go.import("capnproto.org/go/capnp/v3/std/capnp/bytestream");
+$Go.import("capnproto.org/go/capnp/v3/std/capnp/compat/bytestream");

std/capnp/compat/http-over-capnp.capnp

@@ -268,4 +268,4 @@ struct HttpHeader {
 }
 using Go = import "/go.capnp";
 $Go.package("httpovercapnp");
-$Go.import("capnproto.org/go/capnp/v3/std/capnp/httpovercapnp");
+$Go.import("capnproto.org/go/capnp/v3/std/capnp/compat/httpovercapnp");

std/capnp/compat/json-rpc.capnp

@@ -37,10 +37,10 @@ struct RpcMessage {
 
   struct Error {
     code @0 :Int32;
-    message @1 :Text;
+    message @1 :Text $Go.name("messageValue");
     data @2 :Json.Value;
   }
 }
 using Go = import "/go.capnp";
 $Go.package("jsonrpc");
-$Go.import("capnproto.org/go/capnp/v3/std/capnp/jsonrpc");
+$Go.import("capnproto.org/go/capnp/v3/std/capnp/compat/jsonrpc");

std/capnp/compat/json.capnp

@@ -28,7 +28,7 @@ struct Value {
     null @0 :Void;
     boolean @1 :Bool;
     number @2 :Float64;
-    string @3 :Text;
+    string @3 :Text $Go.name("stringValue");
     array @4 :List(Value);
     object @5 :List(Field);
     # Standard JSON values.
@@ -127,4 +127,4 @@ annotation notification @0xa0a054dea32fd98c (method) :Void;
 # Indicates that this method is a JSON-RPC "notification", meaning it expects no response.
 using Go = import "/go.capnp";
 $Go.package("json");
-$Go.import("capnproto.org/go/capnp/v3/std/capnp/json");
+$Go.import("capnproto.org/go/capnp/v3/std/capnp/compat/json");