Label component uniform buffers with their component type name

[stuartparmenter]

Objective

ComponentUniforms<C> creates its buffer without a label. wgpu-core identifies resources in validation errors as Buffer with '<label>' label, so these come out as Buffer with '' label and there is no way to tell which uniform buffer went wrong.

The type_label_buffers feature fills in a type name at the buffer creation site, but it is off in a default build.

Solution

• Sets the buffer label to C's type name in Default for ComponentUniforms<C>.
• Moves set_label and get_label from impl<T: ShaderType + WriteInto> DynamicUniformBuffer<T> to a ShaderType-only block. Neither uses T, so the WriteInto bound was incidental. This keeps Default for ComponentUniforms<C> at C: Component + ShaderType, so nothing breaks and no migration guide is needed.

bevyengine#22698 moved label prepopulation out of constructors because type_name() returns a &'static str while label is an Option<String>, and .to_string() is not const. That only blocks const constructors; this one is not const.

Testing

• cargo check -p bevy, with and without bevy_render/debug.
• cargo fmt --check.

---

This PR was built by me with the assistance of Claude Code w/ Fable 5