Address review comments and add back some #[inline] attrs from removed commits.

Author: michaelwoerister

compiler/rustc_data_structures/src/unord.rs

@@ -159,6 +159,7 @@ impl<T, I: Iterator<Item = T>> UnordItems<T, I> {
         self.collect_stable_ord_by_key(project_to_key)
     }
 
+    #[inline]
     pub fn collect_sorted<HCX, C>(self, hcx: &HCX, cache_sort_key: bool) -> C
     where
         T: ToStableHashKey<HCX>,
@@ -178,6 +179,7 @@ impl<T, I: Iterator<Item = T>> UnordItems<T, I> {
         items
     }
 
+    #[inline]
     pub fn collect_stable_ord_by_key<K, C, P>(self, project_to_key: P) -> C
     where
         K: StableCompare,

compiler/rustc_passes/src/stability.rs

@@ -1052,8 +1052,6 @@ pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
         tcx.dcx().emit_err(errors::UnknownFeature { span, feature: *feature });
     }
 
-    // We only use the hash map contents to emit errors, and the order of
-    // emitted errors do not affect query stability.
     for (&implied_by, &feature) in remaining_implications.to_sorted_stable_ord() {
         let local_defined_features = tcx.lib_features(LOCAL_CRATE);
         let span = local_defined_features