kernel: Remove unused object_address_table.cpp/.h

These source files were entirely unused throughout the rest of the
codebase. This also has the benefit of getting rid of a global variable
as well.

src/core/CMakeLists.txt

@@ -67,8 +67,6 @@ add_library(core STATIC
     hle/kernel/memory.h
     hle/kernel/mutex.cpp
     hle/kernel/mutex.h
-    hle/kernel/object_address_table.cpp
-    hle/kernel/object_address_table.h
     hle/kernel/process.cpp
     hle/kernel/process.h
     hle/kernel/resource_limit.cpp