Update to lockfree 0.2.0

[jmid]

This fixes #35.

• The PR moves the domainslib/ws_deque_test to lockfree - which for now only contains this one data structure.
• The old lock tests are therefore removed.
• Finally it adapts the ws_deque test to test both positively and negatively

[jmid]

I checked locally that this runs without issues on MacOSX on both ocaml trunk commit 7585460 and ocaml PR#11214.
I will therefore merge this and expect the CI to fail until PR#11214 or a similar fix is merged in ocaml trunk.

[jmid]

(the Linux failure happens in the Effect interpretation where an expected error is not found - and is thus unrelated to the lockfree and domainslib changes)