Note when a a move/borrow error is caused by a deref coercion

Fixes rust-lang#73268

When a deref coercion occurs, we may end up with a move error if the
base value has been partially moved out of. However, we do not indicate
anywhere that a deref coercion is occuring, resulting in an error
message with a confusing span.

This PR adds an explicit note to move errors when a deref coercion is
involved. We mention the name of the type that the deref-coercion
resolved to, as well as the `Deref::Target` associated type being used.

Author: Aaron1011

core/src/ops/deref.rs

@@ -63,11 +63,13 @@
 pub trait Deref {
     /// The resulting type after dereferencing.
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_diagnostic_item = "deref_target"]
     type Target: ?Sized;
 
     /// Dereferences the value.
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_diagnostic_item = "deref_method"]
     fn deref(&self) -> &Self::Target;
 }