Userland: Rename Core::Object to Core::EventReceiver

This is a more precise description of what this class actually does.

Userland/Libraries/LibCore/CMakeLists.txt

@@ -12,13 +12,13 @@ set(SOURCES
     EventLoop.cpp
     EventLoopImplementation.cpp
     EventLoopImplementationUnix.cpp
+    EventReceiver.cpp
     File.cpp
     LockFile.cpp
     MappedFile.cpp
     MimeData.cpp
     NetworkJob.cpp
     Notifier.cpp
-    Object.cpp
     Process.cpp
     ProcessStatisticsReader.cpp
     SecretString.cpp