This makes the [New Bevy Renderer](#2535) the default (and only) renderer. The new renderer isn't _quite_ ready for the final release yet, but I want as many people as possible to start testing it so we can identify bugs and address feedback prior to release.
The examples are all ported over and operational with a few exceptions:
* I removed a good portion of the examples in the `shader` folder. We still have some work to do in order to make these examples possible / ergonomic / worthwhile: #3120 and "high level shader material plugins" are the big ones. This is a temporary measure.
* Temporarily removed the multiple_windows example: doing this properly in the new renderer will require the upcoming "render targets" changes. Same goes for the render_to_texture example.
* Removed z_sort_debug: entity visibility sort info is no longer available in app logic. we could do this on the "render app" side, but i dont consider it a priority.
# Objective
The new renderer does not support any options yet for wgpu. These are needed for example for rendering wireframes (see #3193).
## Solution
I've ported WgpuOptions to bevy_render2.
The defaults match the defaults that were used before this PR (meaning, some specific options when target_arch = wasm32).
Additionally, I removed `Auto` from WgpuBackends and added `Primary`. The default will use primary or GL based on the target_arch.
