Merge pull request #834 from embassy-rs/cortex-m-executor-reexport

cortex-m: reexport all items from embassy::executor.

embassy-cortex-m/src/executor.rs

@@ -1,8 +1,7 @@
 //! Executor specific to cortex-m devices.
 use core::marker::PhantomData;
 
-pub use embassy::executor::Executor;
-use embassy::executor::{raw, SendSpawner};
+pub use embassy::executor::*;
 
 use crate::interrupt::{Interrupt, InterruptExt};