TextSpan can not recieve Pointer<Click> events

## What problem does this solve or what need does it fill?

Text can accept Pointer events, but TextSpan cannot. I wanted to make a link inside the large text and I can't implement this with multiple Texts because the layout of the text will be bad.

## What solution would you like?

Add support to recieve Pointer events for TextSpan

## What alternative(s) have you considered?

Provide some other check that the mouse is over a particular TextSpan

## Additional context

```rust
use bevy::prelude::*;

fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_observer(span_observer)
.add_systems(Startup, setup)
.run();

}

fn setup(
mut commands: Commands,
) {
commands.spawn(Camera2d::default());
commands.spawn(
Text::new("")
).with_child(TextSpan::from("text_span"));
}

fn span_observer(
trigger: Trigger>,
q_spans: Query<(Entity, &TextSpan)>,
q_text: Query<(Entity, &Text)>,
) {
if let Ok((e, _)) = q_spans.get(trigger.entity()) {
info!("span_observer {}", e); //never called event if click directly on text span
}

if let Ok((e, _)) = q_text.get(trigger.entity()) {
info!("text_observer {}", e);
}
}
```

```bash
2024-10-18T11:32:03.020663Z INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "Windows 10 Pro", kernel: "19045", cpu: "AMD Ryzen 7 2700X Eight-Core Processor", core_count:
"8", memory: "63.9 GiB" }
2024-10-18T11:32:03.578891Z INFO bevy_render::renderer: AdapterInfo { name: "NVIDIA TITAN Xp", vendor: 4318, device: 6914, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "560.94", backend: Vulkan }
2024-10-18T11:32:04.556414Z INFO bevy_winit::system: Creating new window "App" (0v1#4294967296)
2024-10-18T11:32:08.781002Z INFO bug: text_observer 8v1
```

No source file or test is named. Start by tracing the TextSpan and Text handling for Pointer from the provided reproduction, comparing how each observer target is resolved. Done means clicking a span triggers the observer for that span, with coverage for the shown case.

Written by the indexing model from the issue text.