Add fw dumping

- also fatfs is stupid
- also close files properly on a failed copy
- also check for errors during folder readouts
- also make sure holding vol- doesn't dump the keys anyway

source/tegraexplorer/tools.h

@@ -1,4 +1,5 @@
 #pragma once
 
 void RebootToPayload();
-void TestControllers();
+void TestControllers();
+void DumpSysFw();