Get rid of rustc_query_description!

Queries can provide an arbitrary expression for their description and
their caching behavior. Before, these expressions where stored in a
`rustc_query_description` macro emitted by the `rustc_queries` macro,
and then used in `rustc_query_impl` to fill out the methods for the
`QueryDescription` trait.

Instead, we now emit two new modules from `rustc_queries` containing the
functions with the expressions. `rustc_query_impl` calls these functions
now instead of invoking the macro.

Since we are now defining some of the functions in
`rustc_middle::query`, we now need all the imports for the key types
there as well.

compiler/rustc_query_impl/src/plumbing.rs

@@ -466,7 +466,14 @@ macro_rules! define_queries {
         }
 
         impl<'tcx> QueryDescription<QueryCtxt<'tcx>> for queries::$name<'tcx> {
-            rustc_query_description! { $name }
+            fn describe(tcx: QueryCtxt<'tcx>, key: Self::Key) -> String {
+                ::rustc_middle::query::descs::$name(tcx.tcx, key)
+            }
+
+            #[inline]
+            fn cache_on_disk(tcx: TyCtxt<'tcx>, key: &Self::Key) -> bool {
+                ::rustc_middle::query::cached::$name(tcx, key)
+            }
 
             type Cache = query_storage::$name<'tcx>;