rt: cleanup and simplify scheduler (scheduler v2.5) (#2273)

A refactor of the scheduler internals focusing on simplifying and
reducing unsafety. There are no fundamental logic changes.

* The state transitions of the core task component are refined and
reduced.
* `basic_scheduler` has most unsafety removed.
* `local_set` has most unsafety removed.
* `threaded_scheduler` limits most unsafety to its queue implementation.

1 files changed, 0 insertions, 4 deletions

diff --git a/tokio/src/lib.rs b/tokio/src/lib.rs
index 843a1e64..1498c2b5 100644
--- a/tokio/src/lib.rs
+++ b/tokio/src/lib.rs
@@ -382,10 +382,6 @@ cfg_macros! {
     }
 }
 
-// Tests
-#[cfg(test)]
-mod tests;
-
 // TODO: rm
 #[cfg(feature = "io-util")]
 #[cfg(test)]