feature flag blitz-shell behind a new shell feature on dioxus-native

## Feature Request

~~dioxus-native is tied to winit 0.31.0-beta.2 because blitz-shell is tied to it. bevy 0.19 uses winit 0.30.13. Due to this mismatch, I can't update bevy_dioxus_sync to bevy 0.19.~~

~~However, if blitz-shell and its features were feature flagged and marked optional, this issue would be resolved.~~

edit: On further testing, I realized the issue was me not enabling new rendering feature flags for bevy for when default features are turned off. However, blitz-shell still forces double compiling winit even though the project I'm working on doesn't use it.

Start in the dioxus-native dependency and feature configuration, tracing how blitz-shell brings in winit and how this interacts with bevy_dioxus_sync and Bevy's rendering features. The work is done when blitz-shell can be optional or feature-gated and projects that do not use it no longer compile an unnecessary winit copy; verify with a configuration that disables the relevant default features.

Written by the indexing model from the issue text.