Add timestamps of when tag monitoring dumps are cached

This CL adds a timestamp of when a client's tag monitoring dump is
cached. The timestamp is printed along with the rest of the dump through
`watch dump`.

Bug: 209565054
Test: Manually tested
Change-Id: I4dba62495bdee48ad8ec252cf9c17e974f3f5d86
diff --git a/services/camera/libcameraservice/CameraService.cpp b/services/camera/libcameraservice/CameraService.cpp
index 569ab63..8147701 100644
--- a/services/camera/libcameraservice/CameraService.cpp
+++ b/services/camera/libcameraservice/CameraService.cpp
@@ -4284,12 +4284,20 @@
 
     if (dumpVector.empty()) { return; }
 
+    std::string dumpString;
+
+    String8 currentTime = getFormattedCurrentTime();
+    dumpString += "Cached @ ";
+    dumpString += currentTime.string();
+    dumpString += "\n"; // First line is the timestamp of when client is cached.
+
+
     const String16 &packageName = client->getPackageName();
 
     String8 packageName8 = String8(packageName);
     const char *printablePackageName = packageName8.lockBuffer(packageName.size());
 
-    std::string dumpString;
+
     size_t i = dumpVector.size();
 
     // Store the string in reverse order (latest last)