Fix UI tests

Some UI tests started failing after moving iterator adapters to different modules.

Author: WaffleLapkin

src/test/ui/issues/issue-31173.stderr

@@ -13,11 +13,13 @@ error[E0599]: no method named `collect` found for struct `Cloned<TakeWhile<&mut
 LL |         .collect();
    |          ^^^^^^^ method not found in `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>`
    | 
-  ::: $SRC_DIR/core/src/iter/adapters/mod.rs:LL:COL
+  ::: $SRC_DIR/core/src/iter/adapters/cloned.rs:LL:COL
    |
 LL | pub struct Cloned<I> {
    | -------------------- doesn't satisfy `_: Iterator`
-...
+   | 
+  ::: $SRC_DIR/core/src/iter/adapters/take_while.rs:LL:COL
+   |
 LL | pub struct TakeWhile<I, P> {
    | -------------------------- doesn't satisfy `<_ as Iterator>::Item = &_`
    |

src/test/ui/mismatched_types/issue-36053-2.stderr

@@ -15,7 +15,7 @@ LL |     once::<&str>("str").fuse().filter(|a: &str| true).count();
    |                                       doesn't satisfy `<_ as FnOnce<(&&str,)>>::Output = bool`
    |                                       doesn't satisfy `_: FnMut<(&&str,)>`
    | 
-  ::: $SRC_DIR/core/src/iter/adapters/mod.rs:LL:COL
+  ::: $SRC_DIR/core/src/iter/adapters/filter.rs:LL:COL
    |
 LL | pub struct Filter<I, P> {
    | ----------------------- doesn't satisfy `_: Iterator`