Directory Restructure (#1163)

* Move tests -> testing

* Directory restructure

* Update Cargo.toml during restructure

* Update Makefile during restructure

* Fix arbitrary path

common/hashset_delay/src/lib.rs

@@ -0,0 +1,12 @@
+//! This crate provides a single type (its counter-part HashMapDelay has been removed as it
+//! currently is not in use in lighthouse):
+//! - `HashSetDelay`
+//!
+//! # HashSetDelay
+//!
+//! This is similar to a `HashMapDelay` except the mapping maps to the expiry time. This
+//! allows users to add objects and check their expiry deadlines before the `Stream`
+//! consumes them.
+
+mod hashset_delay;
+pub use crate::hashset_delay::HashSetDelay;