Use generic libpdx event bits facility in libvrflinger and bufferhubd.

Use the generic event bits abstraction to support UDS and ServiceFS
backends properly.

Bug: 34466748
Test: start/stop basicvr repeatedly; observe stable bufferhub counts.
Change-Id: I9f2ea67c25860ad7fb931938991a29a37f3391fc
diff --git a/services/vr/bufferhubd/consumer_channel.cpp b/services/vr/bufferhubd/consumer_channel.cpp
index 4f0ca4e..2264cef 100644
--- a/services/vr/bufferhubd/consumer_channel.cpp
+++ b/services/vr/bufferhubd/consumer_channel.cpp
@@ -27,8 +27,9 @@
 }
 
 ConsumerChannel::~ConsumerChannel() {
-  ALOGD_IF(TRACE, "ConsumerChannel::~ConsumerChannel: channel_id=%d",
-           channel_id());
+  ALOGD_IF(TRACE,
+           "ConsumerChannel::~ConsumerChannel: channel_id=%d buffer_id=%d",
+           channel_id(), buffer_id());
 
   if (auto producer = GetProducer()) {
     if (!handled_)  // Producer is waiting for our Release.