Deprecated Query::many and many_mut (#18183)

# Objective

Alternative to and closes #18120.

Sibling to #18082, see that PR for broader reasoning.

Folks weren't sold on the name `many` (get_many is clearer, and this is
rare), and that PR is much more complex.

## Solution

- Simply deprecate `Query::many` and `Query::many_mut`
- Clean up internal usages

Mentions of this in the docs can wait until it's fully removed in the
0.17 cycle IMO: it's much easier to catch the problems when doing that.

## Testing

CI!

## Migration Guide

`Query::many` and `Query::many_mut` have been deprecated to reduce
panics and API duplication. Use `Query::get_many` and
`Query::get_many_mut` instead, and handle the `Result`.

---------

Co-authored-by: Chris Russell <[email protected]>

Author: alice-i-cecile

crates/bevy_ecs/src/query/mod.rs

@@ -777,7 +777,6 @@ mod tests {
         let _: Option<&Foo> = q.get(e).ok();
         let _: Option<[&Foo; 1]> = q.get_many([e]).ok();
         let _: Option<&Foo> = q.single().ok();
-        let _: [&Foo; 1] = q.many([e]);
         let _: &Foo = q.single().unwrap();
     }
 

crates/bevy_ecs/src/system/query.rs

@@ -1377,6 +1377,7 @@ impl<'w, 's, D: QueryData, F: QueryFilter> Query<'w, 's, D, F> {
     /// - [`get_many`](Self::get_many) for the non-panicking version.
     #[inline]
     #[track_caller]
+    #[deprecated(note = "Use `get_many` instead and handle the Result.")]
     pub fn many<const N: usize>(&self, entities: [Entity; N]) -> [ROQueryItem<'_, D>; N] {
         match self.get_many(entities) {
             Ok(items) => items,
@@ -1682,6 +1683,7 @@ impl<'w, 's, D: QueryData, F: QueryFilter> Query<'w, 's, D, F> {
     /// - [`many`](Self::many) to get read-only query items.
     #[inline]
     #[track_caller]
+    #[deprecated(note = "Use `get_many_mut` instead and handle the Result.")]
     pub fn many_mut<const N: usize>(&mut self, entities: [Entity; N]) -> [D::Item<'_>; N] {
         match self.get_many_mut(entities) {
             Ok(items) => items,