swift

44bd180d - [moveOnly] Add a frontend flag -enable-experimental-move-only to control usage of move only features.

[moveOnly] Add a frontend flag -enable-experimental-move-only to control usage of move only features. These include _move and @_noImplicitCopy. I still need to wire up the parsing of those behind this feature. The reason that I am adding this now is that I am going to now need to make some changes behind a feature flag and I have not yet needed to add one. The specific reason I needed to add one here is to ensure that I properly guard inside _move the call to Builtin.move so as to prevent a "cond_fail" incident. P.S.: This work depends on experimental lexical lifetimes being enabled as well, so I did that at the same time in this PR.