vello_hybrid: Move backends into their own folders

sparse_strips/vello_hybrid/src/render/mod.rs

diff --git a/sparse_strips/vello_hybrid/src/render/mod.rs b/sparse_strips/vello_hybrid/src/render/mod.rs
index 62dfc93..20e215a 100644
--- a/sparse_strips/vello_hybrid/src/render/mod.rs
+++ b/sparse_strips/vello_hybrid/src/render/mod.rs
@@ -9,8 +9,6 @@
 //! - `webgl` contains a WebGL2 backend if the `webgl` feature is active.
 
 pub(crate) mod common;
-#[cfg(all(feature = "webgl", feature = "probe"))]
-mod probe;
 #[cfg(feature = "webgl")]
 mod webgl;
 #[cfg(feature = "wgpu")]
@@ -19,7 +17,7 @@
 pub use common::{Config, GpuStrip, RenderSize};
 
 #[cfg(all(feature = "webgl", feature = "probe"))]
-pub use probe::{WebGlPendingProbe, WebGlProbeError, WebGlProbeStatus};
+pub use webgl::probe::{WebGlPendingProbe, WebGlProbeError, WebGlProbeStatus};
 #[cfg(all(feature = "webgl", feature = "probe"))]
 pub use vello_common::probe::{Probe, ProbeFeature, ProbeResult, ProbeStatistics};
 #[cfg(feature = "webgl")]

sparse_strips/vello_hybrid/src/render/webgl/mod.rs

diff --git a/sparse_strips/vello_hybrid/src/render/webgl.rs b/sparse_strips/vello_hybrid/src/render/webgl/mod.rs
similarity index 99%
rename from sparse_strips/vello_hybrid/src/render/webgl.rs
rename to sparse_strips/vello_hybrid/src/render/webgl/mod.rs
index fee372c..7795d2d 100644
--- a/sparse_strips/vello_hybrid/src/render/webgl.rs
+++ b/sparse_strips/vello_hybrid/src/render/webgl/mod.rs
@@ -20,6 +20,9 @@
 only break in edge cases, and some of them are also only related to conversions from f64 to f32."
 )]
 
+#[cfg(feature = "probe")]
+pub(crate) mod probe;
+
 use crate::draw::ExternalTextureRun;
 use crate::render::common::IMAGE_PADDING;
 use crate::util::RangedSlice;

sparse_strips/vello_hybrid/src/render/webgl/probe.rs

diff --git a/sparse_strips/vello_hybrid/src/render/probe.rs b/sparse_strips/vello_hybrid/src/render/webgl/probe.rs
similarity index 100%
rename from sparse_strips/vello_hybrid/src/render/probe.rs
rename to sparse_strips/vello_hybrid/src/render/webgl/probe.rs

sparse_strips/vello_hybrid/src/render/wgpu/mod.rs

diff --git a/sparse_strips/vello_hybrid/src/render/wgpu.rs b/sparse_strips/vello_hybrid/src/render/wgpu/mod.rs
similarity index 100%
rename from sparse_strips/vello_hybrid/src/render/wgpu.rs
rename to sparse_strips/vello_hybrid/src/render/wgpu/mod.rs