Make moving space compaction concurrent using userfaultfd

Bug: 160737021
Test: art/test/testrunner/testrunner.py
Change-Id: I09d9d49ddb4472a6864fdb7f32da5ffb7bc60c30
(cherry picked from commit 5316aeae5c4bd1757f6d262d162f14368f78c478)
Merged-In: I09d9d49ddb4472a6864fdb7f32da5ffb7bc60c30
12 files changed