Extend track alloc id to show deallocations

[RustyYato]

Currently -Zmiri-track-alloc-id=<id> shows a stack trace of where some memory got allocated, but not where it was deallocated. It would be nice to show where it was deallocated in order to debug use-after-free bugs.

[RalfJung]

That's a good idea, I like it. :)
Currently Miri does not necessarily know when memory gets deallocated, so this will require a new machine hook.

[RalfJung]

@KrishnaSannasi your rustc PR landed, do you plan to follow up on this with a Miri PR? Do you need any help with that?

[RustyYato]

@RalfJung yes, I will follow up with a miri PR, just was a little busy the last few days, I think I can figure this out, but if I need help I'll be sure to ping you. Thanks for all the help so far!