src: do not include internals from node_buffer.h

`node_buffer.h` is a public header, so it should not be using
the `node_internals.h` internal header.

Ref: 290315ace7
Fixes: https://github.com/nodejs/node/issues/15552
PR-URL: https://github.com/nodejs/node/pull/15554
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Andreas Madsen <amwebdk@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

src/node_buffer.h

@@ -22,7 +22,8 @@
 #ifndef SRC_NODE_BUFFER_H_
 #define SRC_NODE_BUFFER_H_
 
-#include "node_internals.h"
+#include "node.h"
+#include "v8.h"
 
 namespace node {
 

src/node_serdes.cc

@@ -1,10 +1,7 @@
-#include "node.h"
+#include "node_internals.h"
 #include "node_buffer.h"
 #include "base-object.h"
 #include "base-object-inl.h"
-#include "env.h"
-#include "env-inl.h"
-#include "v8.h"
 
 namespace node {
 

src/spawn_sync.h

@@ -24,7 +24,7 @@
 
 #if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
 
-#include "node.h"
+#include "node_internals.h"
 #include "node_buffer.h"
 
 namespace node {

src/string_bytes.cc

@@ -22,9 +22,8 @@
 #include "string_bytes.h"
 
 #include "base64.h"
-#include "node.h"
+#include "node_internals.h"
 #include "node_buffer.h"
-#include "v8.h"
 
 #include <limits.h>
 #include <string.h>  // memcpy