Simplify the syntax for macros generated by rustc_queries

- Disallow multiple macros callbacks in the same invocation. In practice, this was never used.
- Remove the `[]` brackets around the macro name
- Require an `ident`, not an arbitrary `tt`

compiler/rustc_query_impl/src/lib.rs

@@ -54,7 +54,7 @@ fn describe_as_module(def_id: LocalDefId, tcx: TyCtxt<'_>) -> String {
     }
 }
 
-rustc_query_append! { [define_queries!] }
+rustc_query_append! { define_queries! }
 
 impl<'tcx> Queries<'tcx> {
     // Force codegen in the dyn-trait transformation in this crate.