Tweak gamepad viewer example style (bevyengine#11484)

# Objective

Since bevyengine#10339, the contrast in this example has been very low. While I
was in there, I made a few other tweaks to the style.

Alternative to bevyengine#10102.

## Solution

- Increase brightness of inactive buttons for higher contrast on the new
clear color
- Combine `DEAD_COLOR` and `EXTENT_COLOR`. These were using the same
value, and combining them might make the intent a little clearer. (This
is the single color for "not the live zone.")
- Make the "stick buttons" slightly smaller, so it's a bit more obvious
that they are sitting inside of the default dead zone.
- Remove explicit text color -- it was the same as the default
- Add top-left margin to the text in the top left, and change the font
size to better match other examples with text in the corner.

## Screenshots

<details>
  <summary>With Bevy's default dead / live zones.</summary>
Before / After


![default](https://github.com/bevyengine/bevy/assets/200550/67bf1f5c-7fc9-4e74-87cf-2a94fcf59a50)
</details>

<details>
<summary>With Bevy's old dead / live zones. (with the upper live zone
boundary != 1.0)</summary>
Before / After


![old](https://github.com/bevyengine/bevy/assets/200550/3aab6a2a-ad57-4749-b2e5-51ed34072b2c)
</details>

examples/tools/gamepad_viewer.rs

@@ -21,12 +21,10 @@ const BUTTONS_Y: f32 = 80.;
 const STICKS_X: f32 = 150.;
 const STICKS_Y: f32 = -135.;
 
-const NORMAL_BUTTON_COLOR: Color = Color::rgb(0.2, 0.2, 0.2);
+const NORMAL_BUTTON_COLOR: Color = Color::rgb(0.3, 0.3, 0.3);
 const ACTIVE_BUTTON_COLOR: Color = Color::PURPLE;
 const LIVE_COLOR: Color = Color::rgb(0.4, 0.4, 0.4);
-const DEAD_COLOR: Color = Color::rgb(0.3, 0.3, 0.3);
-const EXTENT_COLOR: Color = Color::rgb(0.3, 0.3, 0.3);
-const TEXT_COLOR: Color = Color::WHITE;
+const DEAD_COLOR: Color = Color::rgb(0.13, 0.13, 0.13);
 
 #[derive(Component, Deref)]
 struct ReactTo(GamepadButtonType);
@@ -290,7 +288,7 @@ fn setup_sticks(
                 parent.spawn(SpriteBundle {
                     sprite: Sprite {
                         custom_size: Some(Vec2::splat(STICK_BOUNDS_SIZE * 2.)),
-                        color: EXTENT_COLOR,
+                        color: DEAD_COLOR,
                         ..default()
                     },
                     ..default()
@@ -318,7 +316,6 @@ fn setup_sticks(
                 // text
                 let style = TextStyle {
                     font_size: 16.,
-                    color: TEXT_COLOR,
                     ..default()
                 };
                 parent.spawn((
@@ -349,7 +346,7 @@ fn setup_sticks(
                         mesh: meshes.circle.clone(),
                         material: materials.normal.clone(),
                         transform: Transform::from_xyz(0., 0., 5.)
-                            .with_scale(Vec2::splat(0.2).extend(1.)),
+                            .with_scale(Vec2::splat(0.15).extend(1.)),
                         ..default()
                     },
                     MoveWithAxes {
@@ -400,7 +397,6 @@ fn setup_triggers(
                             format!("{:.3}", 0.),
                             TextStyle {
                                 font_size: 16.,
-                                color: TEXT_COLOR,
                                 ..default()
                             },
                         ),
@@ -424,22 +420,30 @@ fn setup_triggers(
 }
 
 fn setup_connected(mut commands: Commands) {
-    let style = TextStyle {
-        color: TEXT_COLOR,
-        font_size: 30.,
+    let text_style = TextStyle {
+        font_size: 20.,
         ..default()
     };
     commands.spawn((
-        TextBundle::from_sections([
-            TextSection {
-                value: "Connected Gamepads:\n".to_string(),
-                style: style.clone(),
-            },
-            TextSection {
-                value: "None".to_string(),
-                style,
+        TextBundle {
+            text: Text::from_sections([
+                TextSection {
+                    value: "Connected Gamepads:\n".to_string(),
+                    style: text_style.clone(),
+                },
+                TextSection {
+                    value: "None".to_string(),
+                    style: text_style,
+                },
+            ]),
+            style: Style {
+                position_type: PositionType::Absolute,
+                top: Val::Px(12.),
+                left: Val::Px(12.),
+                ..default()
             },
-        ]),
+            ..default()
+        },
         ConnectedGamepadsText,
     ));
 }