Enable ASAN poisoning in internal tests

Summary:
I didn't want ASAN poisoning to be enabled by default (to avoid breaking existing ASAN tiers), so it's opt in.  However we want to opt all our tests into ASAN poisoning to catch regressions.

Define a new BUCK rule called `cachelib_cpp_unittest` that defines a PP macro.  That macro will enable ASAN poisoning for those tests.

Also automatically set the oncall field for tests.

This diff changes *all* cpp_unittest rules in Cachelib to use the new rule.

Reviewed By: AlnisM

Differential Revision: D104668331

fbshipit-source-id: 79de1d7fc3da36a489910d89d0c346a36cb617bd

Author: rlyerly

cachelib/allocator/CacheAllocatorConfig.h

@@ -749,9 +749,13 @@ class CacheAllocatorConfig {
 
 #if FOLLY_SANITIZE_ADDRESS
   // If true, slab memory is ASAN-poisoned on free and unpoisoned on allocation.
-  // Disabled by default to avoid overhead in ASAN builds. Enable for testing
-  // or when actively debugging memory issues.
+#ifdef CACHELIB_TEST_BUILD
+  // Enabled by default in test builds
+  bool enableSlabAsanPoisoning{true};
+#else
+  // Disabled by default in production ASAN builds to avoid overhead.
   bool enableSlabAsanPoisoning{false};
+#endif
 #endif
 
   friend CacheT;