Add support for miri to the codebase

[cwfitzgerald]

Wires in support for miri (and potentially ASAN) in the codebase.

Main transform was manually enumerating tests.

[andyleiserson]

This is really nice to have, thank you!

It is too bad to lose the implicit test enumeration, especially because the macro suppresses the dead code warning if you forget to add a test to the list. But I think we can land this change and worry about improvements later.

I played with a macro a bit and came up with this, but it doesn't handle the wasm case (or run_sync, but that shouldn't be hard).

[andyleiserson]

There is a commented test in this file, it might be worth putting a reminder by the commented test that it needs to be added to the test list if restored.