kernel: Move object class to its own source files

General moving to keep kernel object types separate from the direct
kernel code. Also essentially a preliminary cleanup before eliminating
global kernel state in the kernel code.

src/core/CMakeLists.txt

@@ -123,6 +123,8 @@ add_library(core STATIC
     hle/kernel/memory.h
     hle/kernel/mutex.cpp
     hle/kernel/mutex.h
+    hle/kernel/object.cpp
+    hle/kernel/object.h
     hle/kernel/process.cpp
     hle/kernel/process.h
     hle/kernel/resource_limit.cpp