Add bevy_transform benchmarks (#23906)

# Objective

- Add dedicated benchmarks for `bevy_transform`'s propagation systems to
catch performance regressions.

## Solution

**Benchmarks** (`benches/benches/bevy_transform/propagate.rs`):

Added small benchmarks targeting each stage of the propagation pipeline
individually.

- `mark_dirty_trees` — localized vs. distributed leaf update patterns
- `propagate_parent_transforms` — full recompute with roots changed vs.
leaves changed (static optimization disabled to isolate traversal cost)
- `transform_pipeline` — end-to-end pipeline with static optimization
on/off, plus `ChildOf` reparent churn

The hierarchy setup uses 48 roots × 6 depth layers with mixed fanout
(4-4-3-3-2-2) and extra archetype padding (`MarkerA/B/C`) to reflect
realistic gameplay scenes.

## Testing

```sh
cargo bench -p benches --bench transform
```

---------

Co-authored-by: ickshonpe <27962798+ickshonpe@users.noreply.github.com>

Author: Sieluna

benches/Cargo.toml

@@ -26,6 +26,7 @@ bevy_asset = { path = "../crates/bevy_asset" }
 bevy_render = { path = "../crates/bevy_render" }
 bevy_scene = { path = "../crates/bevy_scene" }
 bevy_tasks = { path = "../crates/bevy_tasks" }
+bevy_transform = { path = "../crates/bevy_transform" }
 bevy_ui = { path = "../crates/bevy_ui" }
 bevy_platform = { path = "../crates/bevy_platform", default-features = false, features = [
   "std",
@@ -110,3 +111,8 @@ harness = false
 name = "tasks"
 path = "benches/bevy_tasks/main.rs"
 harness = false
+
+[[bench]]
+name = "transform"
+path = "benches/bevy_transform/main.rs"
+harness = false

benches/benches/bevy_transform/main.rs

@@ -0,0 +1,5 @@
+use criterion::criterion_main;
+
+mod propagate;
+
+criterion_main!(propagate::benches);