move bevy_core_pipeline to dev-dependencies

[jakobhellermann]

bevy_core_pipeline is only used in the render to texture example

[jakobhellermann]

I found this while looking into potential compile time improvements. Would you be open to depending on bevy crates directly? That way, on a clean compile, bevy_egui could compile immediately after bevy_render in parallel with bevy_pbr and potentially a lot of other bevy helper crates.

In this example it would save 2 seconds:

I can open a PR if you want.

[mvlabat]

Great find, thank you!

Would you be open to depending on bevy crates directly?

I was hesitant about depending on subcrates, as it makes patching more cumbersome for fork users. But compile times surely have higher priority, so if the gains are significant, I'm 100% open to this.