Add a service-unique ID to BufferNode

All the BufferNode allocated by bufferhub hwservice now will have a
unique ID generated and managed by the UniqueIdGenerator.

The idGenerator is placed in global static namespace because 1)
therefore it is process-unique 2) BufferNode could still access it
without a reference to the service instance.

Added UniqueIdGenerator_test.

Test: UniqueIdGenerator_test, BufferNode_test, buffer_hub-test,
BufferHubBuffer_test passed.
Fix: 118844348
Change-Id: I9c9adebab3af7b9de71dbe8728d3f24ed231338d
diff --git a/services/bufferhub/BufferHubService.cpp b/services/bufferhub/BufferHubService.cpp
index 3bfd9cb..fc5ad1d 100644
--- a/services/bufferhub/BufferHubService.cpp
+++ b/services/bufferhub/BufferHubService.cpp
@@ -35,7 +35,7 @@
 
     std::shared_ptr<BufferNode> node =
             std::make_shared<BufferNode>(desc.width, desc.height, desc.layers, desc.format,
-                                         desc.usage, userMetadataSize);
+                                         desc.usage, userMetadataSize, nodeIdGenerator.getId());
     if (node == nullptr || !node->IsValid()) {
         ALOGE("%s: creating BufferNode failed.", __FUNCTION__);
         _hidl_cb(/*bufferClient=*/nullptr, /*status=*/BufferHubStatus::ALLOCATION_FAILED);