Make gcore a std library and remove std, alloc, and more unused features (#2724)

* gcore: remove features `std`, `alloc`, `gpu` and `reflections`, now always available

* gcore: remove non-working features `kurbo` and `log`

node-graph/gcore/src/raster.rs

@@ -287,9 +287,7 @@ impl<T: BitmapMut + Bitmap> BitmapMut for &mut T {
 	}
 }
 
-#[cfg(feature = "alloc")]
 pub use self::image::Image;
-#[cfg(feature = "alloc")]
 pub mod image;
 
 trait SetBlendMode {