Improve component registration performance (#18180)

# Objective

Make component registration faster. This is a tinny, almost petty PR,
but it led to roughly 10% faster registration, according to my
benchmarks in #17871.

Up to y'all if we do this or not. It is completely unnecessary, but its
such low hanging fruit that I wanted to put it out there.

## Solution

Instead of cloning a `HashSet`, collect it into a `SmallVec`. Since this
is empty for many components, this saves a lot of allocation and hashing
work.

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

crates/bevy_ecs/src/component.rs

@@ -34,6 +34,7 @@ use core::{
     ops::{Deref, DerefMut},
 };
 use disqualified::ShortName;
+use smallvec::SmallVec;
 use thiserror::Error;
 
 /// A data type that can be used to store data for an [entity].
@@ -2067,7 +2068,10 @@ impl Components {
         required_components.0.extend(required_components_tmp.0);
 
         // Propagate the new required components up the chain to all components that require the requiree.
-        if let Some(required_by) = self.get_required_by(requiree).cloned() {
+        if let Some(required_by) = self
+            .get_required_by(requiree)
+            .map(|set| set.iter().copied().collect::<SmallVec<[ComponentId; 8]>>())
+        {
             // `required` is now required by anything that `requiree` was required by.
             self.get_required_by_mut(required)
                 .unwrap()