aapt2: add 'dump overlayable' command

Add a command to print a resource table's <overlayable> resources. Given
the following input

  <overlayable name="TestResources">
    <policy type="system">
      <item type="string" name="a" />
    </policy>
    <policy type="sytem|vendor">
      <item type="string" name="b" />
      <item type="string" name="c" />
    </policy>
  </overlayable>

aapt2 dump overlayable will produce

  name="TestResources" actor=""
    policies="system"
      string/a
    policies="system|vendor"
      string/b
      string/c

Bug: 120609160
Test: manual (aapt2 dump overlayable $(gettop)/frameworks/base/cmds/idmap2/tests/data/target/target.apk)
Change-Id: I21041e6169c62d01f1a469624911ce7cad3e18a8
diff --git a/tools/aapt2/cmd/Dump.cpp b/tools/aapt2/cmd/Dump.cpp
index 429aff1..3982d12 100644
--- a/tools/aapt2/cmd/Dump.cpp
+++ b/tools/aapt2/cmd/Dump.cpp
@@ -394,6 +394,17 @@
   return 0;
 }
 
+int DumpOverlayableCommand::Dump(LoadedApk* apk) {
+  ResourceTable* table = apk->GetResourceTable();
+  if (!table) {
+    GetDiagnostics()->Error(DiagMessage() << "Failed to retrieve resource table");
+    return 1;
+  }
+
+  Debug::DumpOverlayable(*table, GetPrinter());
+  return 0;
+}
+
 const char DumpBadgerCommand::kBadgerData[2925] = {
     32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,
     32,  32,  32,  32,  32,  32,  95,  46,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,  32,