[incremental] expose duration since oldest pending read

As requested by go/incremental-disablement-metrics, we will expose the
duration since oldest pending read as part of the crash/ANR metrics.
This is the first step that exposes the value to Incremental Service.

BUG: 180951530
Test: unit test
Change-Id: Ic67460072556ef01780a1794b40924ca2092060d
diff --git a/services/incremental/BinderIncrementalService.cpp b/services/incremental/BinderIncrementalService.cpp
index 42360d8..8f12b2e 100644
--- a/services/incremental/BinderIncrementalService.cpp
+++ b/services/incremental/BinderIncrementalService.cpp
@@ -348,6 +348,12 @@
     return ok();
 }
 
+binder::Status BinderIncrementalService::getMetrics(int32_t storageId,
+                                                    android::os::PersistableBundle* _aidl_return) {
+    mImpl.getMetrics(storageId, _aidl_return);
+    return ok();
+}
+
 } // namespace android::os::incremental
 
 jlong Incremental_IncrementalService_Start(JNIEnv* env) {