Verify that allocated memory is always zeroed.

If this is a low ram device, then do not run these tests. Otherwise,
verify that memory returned from the allocator is zero.

Bug: 171429763
Bug: 264539505
Bug: 265431478

Test: New unit tests pass on scudo.
Test: New unit tests fail on original jemalloc.
Test: New unit tests pass on jemalloc that always zeroes memory.
Test: New unit tests are skipped on low ram device.
Test: Ran unit tests atest CtsBionicTestCases in above scenarios.
Change-Id: Id62ab74f649c0f7c14a951235fe79972926ecec0
diff --git a/tests/utils.h b/tests/utils.h
index 81869e3..2e00cc1 100644
--- a/tests/utils.h
+++ b/tests/utils.h
@@ -313,3 +313,5 @@
   return false;
 #endif
 }
+
+bool IsLowRamDevice();