AddressSanitizer support for workspaces

[ripatel-fd]

Firedancer primarily allocates memory in shared memory workspaces (fd_wksp.h). These are mapped into memory as part of large shared memory objects.

ASan currently fails to detect most forms of out-of-bounds memory accesses because it considers an entire mmap()ed shared memory object as valid.

To fix, use the ASan poison API (https://github.com/firedancer-io/firedancer/issues/39) to mark workspaces invalid by default. Then, selectively unpoison when a user joins or creates objects in workspace memory regions.

[ripatel-fd]

https://git.firedancer.io/c/firedancer/+/412

[ripatel-fd]

Fixed by https://github.com/firedancer-io/firedancer/pull/50

[ripatel-fd]

@lheeger-jump Are you still working on this?