use associated type bounds in QueryManyIter and QueryIter::sort() (#14107)

# Objective

The bounds for query iterators are quite intimidating.

## Solution

With Rust 1.79, [associated type
bounds](rust-lang/rust#122055) stabilized,
which can simplify the bounds slightly.

Author: Victoronz

crates/bevy_ecs/src/query/iter.rs

@@ -279,18 +279,15 @@ impl<'w, 's, D: QueryData, F: QueryFilter> QueryIter<'w, 's, D, F> {
     /// # schedule.add_systems((system_1, system_2, system_3));
     /// # schedule.run(&mut world);
     /// ```
-    pub fn sort<L: ReadOnlyQueryData + 'w>(
+    pub fn sort<L: ReadOnlyQueryData<Item<'w>: Ord> + 'w>(
         self,
     ) -> QuerySortedIter<
         'w,
         's,
         D,
         F,
         impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w,
-    >
-    where
-        L::Item<'w>: Ord,
-    {
+    > {
         // On the first successful iteration of `QueryIterationCursor`, `archetype_entities` or `table_entities`
         // will be set to a non-zero value. The correctness of this method relies on this.
         // I.e. this sort method will execute if and only if `next` on `QueryIterationCursor` of a
@@ -376,18 +373,15 @@ impl<'w, 's, D: QueryData, F: QueryFilter> QueryIter<'w, 's, D, F> {
     /// # schedule.add_systems((system_1));
     /// # schedule.run(&mut world);
     /// ```
-    pub fn sort_unstable<L: ReadOnlyQueryData + 'w>(
+    pub fn sort_unstable<L: ReadOnlyQueryData<Item<'w>: Ord> + 'w>(
         self,
     ) -> QuerySortedIter<
         'w,
         's,
         D,
         F,
         impl ExactSizeIterator<Item = Entity> + DoubleEndedIterator + FusedIterator + 'w,
-    >
-    where
-        L::Item<'w>: Ord,
-    {
+    > {
         // On the first successful iteration of `QueryIterationCursor`, `archetype_entities` or `table_entities`
         // will be set to a non-zero value. The correctness of this method relies on this.
         // I.e. this sort method will execute if and only if `next` on `QueryIterationCursor` of a
@@ -1083,10 +1077,7 @@ impl<'w, 's, D: QueryData, F: QueryFilter, I: Iterator<Item = Entity>> Debug
 /// Entities that don't match the query are skipped.
 ///
 /// This struct is created by the [`Query::iter_many`](crate::system::Query::iter_many) and [`Query::iter_many_mut`](crate::system::Query::iter_many_mut) methods.
-pub struct QueryManyIter<'w, 's, D: QueryData, F: QueryFilter, I: Iterator>
-where
-    I::Item: Borrow<Entity>,
-{
+pub struct QueryManyIter<'w, 's, D: QueryData, F: QueryFilter, I: Iterator<Item: Borrow<Entity>>> {
     entity_iter: I,
     entities: &'w Entities,
     tables: &'w Tables,
@@ -1096,9 +1087,8 @@ where
     query_state: &'s QueryState<D, F>,
 }
 
-impl<'w, 's, D: QueryData, F: QueryFilter, I: Iterator> QueryManyIter<'w, 's, D, F, I>
-where
-    I::Item: Borrow<Entity>,
+impl<'w, 's, D: QueryData, F: QueryFilter, I: Iterator<Item: Borrow<Entity>>>
+    QueryManyIter<'w, 's, D, F, I>
 {
     /// # Safety
     /// - `world` must have permission to access any of the components registered in `query_state`.
@@ -1196,10 +1186,8 @@ where
     }
 }
 
-impl<'w, 's, D: ReadOnlyQueryData, F: QueryFilter, I: Iterator> Iterator
+impl<'w, 's, D: ReadOnlyQueryData, F: QueryFilter, I: Iterator<Item: Borrow<Entity>>> Iterator
     for QueryManyIter<'w, 's, D, F, I>
-where
-    I::Item: Borrow<Entity>,
 {
     type Item = D::Item<'w>;
 
@@ -1216,16 +1204,13 @@ where
 }
 
 // This is correct as [`QueryManyIter`] always returns `None` once exhausted.
-impl<'w, 's, D: ReadOnlyQueryData, F: QueryFilter, I: Iterator> FusedIterator
+impl<'w, 's, D: ReadOnlyQueryData, F: QueryFilter, I: Iterator<Item: Borrow<Entity>>> FusedIterator
     for QueryManyIter<'w, 's, D, F, I>
-where
-    I::Item: Borrow<Entity>,
 {
 }
 
-impl<'w, 's, D: QueryData, F: QueryFilter, I: Iterator> Debug for QueryManyIter<'w, 's, D, F, I>
-where
-    I::Item: Borrow<Entity>,
+impl<'w, 's, D: QueryData, F: QueryFilter, I: Iterator<Item: Borrow<Entity>>> Debug
+    for QueryManyIter<'w, 's, D, F, I>
 {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.debug_struct("QueryManyIter").finish()