Migrate examples using text based UI to feathers

Many old examples used a combination of text and hardcoded key presses as a UI because bevy_ui was too much trouble. Now that we have feathers and bsn we can migrate them to use an actual UI.

Here's a list of all the rendering related examples using this pattern sorted by how many controls would need to be migrated.

## Low - only 1 control to migrate

- `3d/clearcoat.rs`
- `3d/occlusion_culling.rs`
- `3d/specular_tint.rs`

## Medium - 2 to 4 controls to migrate

- `2d/2d_shapes.rs`
- `2d/wireframe_2d.rs`
- `3d/3d_shapes.rs`
- `3d/anisotropy.rs`
- `3d/atmospheric_fog.rs`
- `3d/auto_exposure.rs`
- `3d/blend_modes.rs`
- `3d/deferred_rendering.rs`
- `3d/depth_of_field.rs`
- `3d/generate_custom_mesh.rs`
- `3d/irradiance_volumes.rs`
- `3d/motion_blur.rs`
- `3d/parallax_mapping.rs`
- `3d/post_processing.rs`
- `3d/rect_light.rs`
- `3d/reflection_probes.rs`
- `3d/solari.rs`
- `3d/ssao.rs`
- `3d/visibility_range.rs`
- `3d/volumetric_fog.rs`
- `gizmos/light_gizmos.rs`
- `gizmos/transform_gizmo.rs`

## High - 5 or more controls to migrate

- `2d/bloom_2d.rs`
- `3d/anti_aliasing.rs`
- `3d/bloom_3d.rs`
- `3d/fog.rs`
- `3d/lighting.rs`
- `3d/shadow_biases.rs`
- `3d/tonemapping.rs`
- `3d/transmission.rs`
- `3d/wireframe.rs`
- `gizmos/2d_gizmos.rs`
- `gizmos/3d_gizmos.rs`

This is not an exhaustive list, there's likely more than that.

Start with one low-scope example such as examples/3d/clearcoat.rs and inspect how its text controls and hardcoded key presses work. Read the existing feathers and bsn usage before migrating that control to an actual UI. Done means the example uses the new UI for its control and no longer relies on the old text-and-key-press pattern.

Written by the indexing model from the issue text.