Run tests under Miri

[complexspaces]

This is what the issue title describes. We shouldn't have any undefined behavior in the code, but running Miri is fast enough and easy to configure so it'd be worthwhile adding it just as a precautionary measure.

Additionally, a flag such as -Zmiri-track-alloc-accesses and Miri's allocation emulation/tracking functionality could be another automated tool to ensure we see the intended writes to the memory being zeroized.