build: rust asan builds and regress tests

Let's add a rust nightly canary debug build with address sanitizers, run regress tests if possible. 

Rationale:
- we've experienced at least 2 weird panicks in production which looked like they were statically impossible
  - did not reproduce in the fleet

Related to earlier:

- https://github.com/neondatabase/neon/issues/536
- https://github.com/neondatabase/neon/issues/6053

