Add support for debug groups

[mvaligursky]

I have my draw calls / render passes and similar wrapped in useful debug groups, it'd be fantastic to see the list of captured Commands to use those to create sub-hierarchies, instead of a flat list.

https://toji.dev/webgpu-best-practices/error-handling#debug-groups

[takahirox]

That sounds like a nice idea. I want to improve the layout.

PRs are very welcome.