Revert "Move ScopedFd from libcore to libnativehelper (part 2)"

This reverts commit 8028fe9fb10e715e68b11d549ba8518053d33ef8.
Revert "Move more utility classes from libcore to libnativehelper (part 2)"

This reverts commit 7785a7b343822198e043339a976c7f3564fa43fb.