In BF-31940, we found that an innocuous allocation was continually causing a segfault when it was randomly selected for sampling by the tcmalloc allocation sampler.

The bug originates inside the implementation of abseil's stack unwinding utility here (on x86 only), which is called for each sampled allocation. I think that we should just wholesale disable allocation sampling by default in tcmalloc-- we do not utilize it outside of the heap profiler, which will set the sampling rate on its own already, and disabling it could also create some (very minor) perf benefits.