Split Futures exceptions by Promise vs Future

Summary:
[Folly] Split Futures exceptions by `Promise` vs `Future`.

* Move `Promise` exceptions into the `Promise` header.
* Move `Future` exceptions into the `Future` header.
* Split `NoState` into `PromiseInvalid` and `FutureInvalid`.
* Remove the newly-empty exceptions header.

Reviewed By: andriigrynenko

Differential Revision: D7966499

fbshipit-source-id: 2dc6d2a941493979ebf47b3e70e5cf6a6fbd33cf

hphp/runtime/ext/watchman/ext_watchman.cpp

@@ -433,7 +433,7 @@ struct ActiveSubscription {
     auto res_future = promise.getFuture();
     if (timeout != std::chrono::milliseconds::zero()) {
       res_future = res_future.within(timeout)
-        .onError([](folly::TimedOut) {
+        .onError([](folly::FutureTimeout) {
           return false;
         });
     }