Accept a file descriptor to write bugreport file

This will be used via the bugreporting api.

Changed dumpstate to do bugreport generation in its own directory
in the beginning and to copy over to the destination fd or directory
at the very end.

BUG: 111441001
Test: adb bugreport
Test: adb shell /data/nativetest64/dumpstate_test/dumpstate_test
Test: interactive bugreport
Change-Id: I83e24f0989a202e84266b6e0fdf8edc14ea639bf