tombstoned: Add a shared library version of libtombstoned_client...

.. for ART and the frameworks to link against. In the new stack dumping
scheme (see related bug), the Java runtime will communicate with
tombstoned in order to obtain a FD to which it can write its traces.

Also move things around to separate headers that are private
implementation details from headers that constitute the public debuggerd
API. There are currently only three such headers :

- tombstoned/tombstoned.h
- debuggerd/client.h
- debuggerd/handler.h

Bug: 32064548
Test: make

Change-Id: If1b8578550e373d84828b180bbe585f1088d1aa3
diff --git a/debuggerd/debuggerd_test.cpp b/debuggerd/debuggerd_test.cpp
index 0b4bbfb..f17724a 100644
--- a/debuggerd/debuggerd_test.cpp
+++ b/debuggerd/debuggerd_test.cpp
@@ -35,12 +35,13 @@
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
 #include <cutils/sockets.h>
-#include <debuggerd/handler.h>
-#include <debuggerd/protocol.h>
-#include <debuggerd/tombstoned.h>
-#include <debuggerd/util.h>
 #include <gtest/gtest.h>
 
+#include "debuggerd/handler.h"
+#include "protocol.h"
+#include "tombstoned/tombstoned.h"
+#include "util.h"
+
 using namespace std::chrono_literals;
 using android::base::unique_fd;