refactor(lib): Switch from pin-project to pin-project-lite (#2566)

Note the practical affects of this change:

- Dependency count with --features full dropped from 65 to 55.
- Time to compile after a clean dropped from 48s to 35s (on a pretty underpowered VM).

Closes #2388

src/client/pool.rs

@@ -11,7 +11,7 @@ use futures_channel::oneshot;
 use tokio::time::{Duration, Instant, Interval};
 
 use super::client::Ver;
-use crate::common::{task, exec::Exec, Future, Pin, Poll, Unpin};
+use crate::common::{exec::Exec, task, Future, Pin, Poll, Unpin};
 
 // FIXME: allow() required due to `impl Trait` leaking types to this lint
 #[allow(missing_debug_implementations)]
@@ -714,16 +714,17 @@ impl Expiration {
 }
 
 #[cfg(feature = "runtime")]
-#[pin_project::pin_project]
-struct IdleTask<T> {
-    #[pin]
-    interval: Interval,
-    pool: WeakOpt<Mutex<PoolInner<T>>>,
-    // This allows the IdleTask to be notified as soon as the entire
-    // Pool is fully dropped, and shutdown. This channel is never sent on,
-    // but Err(Canceled) will be received when the Pool is dropped.
-    #[pin]
-    pool_drop_notifier: oneshot::Receiver<crate::common::Never>,
+pin_project_lite::pin_project! {
+    struct IdleTask<T> {
+        #[pin]
+        interval: Interval,
+        pool: WeakOpt<Mutex<PoolInner<T>>>,
+        // This allows the IdleTask to be notified as soon as the entire
+        // Pool is fully dropped, and shutdown. This channel is never sent on,
+        // but Err(Canceled) will be received when the Pool is dropped.
+        #[pin]
+        pool_drop_notifier: oneshot::Receiver<crate::common::Never>,
+    }
 }
 
 #[cfg(feature = "runtime")]
@@ -776,7 +777,7 @@ mod tests {
     use std::time::Duration;
 
     use super::{Connecting, Key, Pool, Poolable, Reservation, WeakOpt};
-    use crate::common::{task, exec::Exec, Future, Pin};
+    use crate::common::{exec::Exec, task, Future, Pin};
 
     /// Test unique reservations.
     #[derive(Debug, PartialEq, Eq)]