Support nested messages, fix casing. Support test-cases in packages.

betterproto/tests/inputs/nestedtwice/nestedtwice.json

@@ -1,10 +1,10 @@
 {
-  "root": {
+  "top": {
     "name": "double-nested",
-    "parent": {
-      "child": [{"foo": "hello"}],
-      "enumChild": ["A"],
-      "rootParentChild": [{"a": "hello"}],
+    "middle": {
+      "bottom": [{"foo": "hello"}],
+      "enumBottom": ["A"],
+      "topMiddleBottom": [{"a": "hello"}],
       "bar": true
     }
   }

betterproto/tests/inputs/nestedtwice/nestedtwice.proto

@@ -1,26 +1,26 @@
 syntax = "proto3";
 
 message Test {
-  message Root {
-    message Parent {
-      message RootParentChild {
+  message Top {
+    message Middle {
+      message TopMiddleBottom {
         string a = 1;
       }
-      enum EnumChild{
+      enum EnumBottom{
         A = 0;
         B = 1;
       }
-      message Child {
+      message Bottom {
         string foo = 1;
       }
       reserved 1;
-      repeated Child child = 2;
-      repeated EnumChild enumChild=3;
-      repeated RootParentChild rootParentChild=4;
+      repeated Bottom bottom = 2;
+      repeated EnumBottom enumBottom=3;
+      repeated TopMiddleBottom topMiddleBottom=4;
       bool bar = 5;
     }
     string name = 1;
-    Parent parent = 2;
+    Middle middle = 2;
   }
-  Root root = 1;
+  Top top = 1;
 }