[asan] more performance to FakeStack: a) don't used atomic exchange, instead rely on regular load and store and other signal-safe logic; b) remove allocated_from_size_class_mask_ which is not helping much anyway; Another 10% speedup

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190664 91177308-0d34-0410-b5e6-96231b3b80d8