Add API to BpBinder to get handle for debugging

This is the local handle for the process requesting it.

Test: build
Change-Id: I87df46d166bf5041972624af42369a76adb52ee9
diff --git a/libs/binder/BpBinder.cpp b/libs/binder/BpBinder.cpp
index 765e21c..55566e2 100644
--- a/libs/binder/BpBinder.cpp
+++ b/libs/binder/BpBinder.cpp
@@ -188,6 +188,14 @@
     return std::get<BinderHandle>(mHandle).handle;
 }
 
+std::optional<int32_t> BpBinder::getDebugBinderHandle() const {
+    if (!isRpcBinder()) {
+        return binderHandle();
+    } else {
+        return std::nullopt;
+    }
+}
+
 bool BpBinder::isDescriptorCached() const {
     Mutex::Autolock _l(mLock);
     return mDescriptorCache.size() ? true : false;