Move core data structure of DetachedBuffer into BufferNode

1/ Supports mutiple DetachedBuffer(s) to be created from a single
BufferNode.
2/ Separate core data structure and logic (i.e. BufferNode) out of the
IPC layer (i.e. DetachedBufferChannel).
3/ DetachedBufferChannel will be renamed to BufferChannel in future
and becomes the universal backend of GraphicBuffer. Thus we are naming
the new class BufferNode instead of DetachedBufferNode.
4/ Move BufferHubDefs out of bufferhub_rpc.h, as BufferHubDefs is not
directly related to the PDX IPCm echanism.

Bug: 112011098
Bug: 112012812
Bug: 111976433
Bug: 70046255
Test: buffer_hub-test
Change-Id: Ieba19329a0e823c78f21611462dedacdad3aab85
diff --git a/services/vr/bufferhubd/buffer_hub.cpp b/services/vr/bufferhubd/buffer_hub.cpp
index e57c8ed..c0ee31b 100644
--- a/services/vr/bufferhubd/buffer_hub.cpp
+++ b/services/vr/bufferhubd/buffer_hub.cpp
@@ -13,8 +13,8 @@
 
 #include <pdx/default_transport/service_endpoint.h>
 #include <private/dvr/bufferhub_rpc.h>
+#include "buffer_channel.h"
 #include "consumer_channel.h"
-#include "detached_buffer_channel.h"
 #include "producer_channel.h"
 #include "producer_queue_channel.h"
 
@@ -267,7 +267,7 @@
       return {};
 
     case DetachedBufferRPC::Promote::Opcode:
-      // In addition to the message handler in the DetachedBufferChannel's
+      // In addition to the message handler in the BufferChannel's
       // HandleMessage method, we also need to invalid the channel. Note that
       // this has to be done after HandleMessage returns to make sure the IPC
       // request has went back to the client first.
@@ -332,9 +332,9 @@
     return ErrorStatus(EALREADY);
   }
 
-  std::unique_ptr<DetachedBufferChannel> channel =
-      DetachedBufferChannel::Create(this, buffer_id, width, height, layer_count,
-                                    format, usage, user_metadata_size);
+  std::unique_ptr<BufferChannel> channel =
+      BufferChannel::Create(this, buffer_id, width, height, layer_count, format,
+                            usage, user_metadata_size);
   if (!channel) {
     ALOGE(
         "BufferHubService::OnCreateDetachedBuffer: Failed to allocate buffer, "