Refactor includes structure, getting rid of rust_internal.h

Many changes to code structure are included:
- removed TIME_SLICE_IN_MS
- removed sychronized_indexed_list
- removed region_owned
- kernel_owned move to kernel.h, task_owned moved to task.h
- global configs moved to rust_globals.h
- changed #pragma once to standard guard in rust_upcall.h
- got rid of memory.h

src/rt/rust_env.cpp

@@ -3,7 +3,7 @@
 // that might come from the environment is loaded here, once, during
 // init.
 
-#include "rust_internal.h"
+#include "rust_env.h"
 
 // The environment variables that the runtime knows about
 #define RUST_THREADS "RUST_THREADS"