Adjust diagnostic items for mpmc/mpsc Receiver and Sender

`MpscReceiver` aligns with `MpscSender`.  The original name appears to
not actually have been in use, for better or worse.

Along the way, sprinkle the attribute onto `mpmc::Receiver` and
`mpmc::Sender` too.

Author: cammeresi

clippy_utils/src/sym.rs

@@ -90,6 +90,10 @@ generate! {
     MAX,
     MIN,
     MaybeDef,
+    MpmcReceiver,
+    MpmcSender,
+    MpscReceiver,
+    MpscSender,
     MsrvStack,
     Octal,
     OpenOptions,
@@ -99,7 +103,6 @@ generate! {
     PathBuf,
     PathLookup,
     RangeBounds,
-    Receiver,
     RefCellRef,
     RefCellRefMut,
     Regex,

clippy_utils/src/ty/mod.rs

@@ -192,7 +192,8 @@ pub fn has_iter_method(cx: &LateContext<'_>, probably_ref_ty: Ty<'_>) -> Option<
         sym::HashMap,
         sym::PathBuf,
         sym::Path,
-        sym::Receiver,
+        sym::MpscReceiver,
+        sym::MpmcReceiver,
     ];
 
     let ty_to_check = match probably_ref_ty.kind() {