Group glow config in a struct (#8108)

This is a breaking public API change, but is otherwise trivial due to it
not changing any actual runtime behaviour.

This renames eframe's NativeOptions `vsync` option to `glow_vsync` to
make clear without even looking at docs fully that this is specific to
the `glow` backend.

While I think a better option would actually be to change the wgpu
creation options to match the vsync option if not specified (either to
`AutoVsync` or `AutoNoVsync` depending on setting) this would require
this be made an `Option<PresentMode>`, which would be confusing - and
the `WgpuConfiguration` should probably take priority over other options
here, as there's more than 2 present modes that are relevant. So I think
this is a suitable way to go.

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* This does not close an issue - this was a trivial amount of code to
change, so I might as well just make it a PR on the spot.
* [x] I have followed the instructions in the PR template

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/eframe/src/web/web_painter_glow.rs

@@ -31,8 +31,13 @@ impl WebPainterGlow {
         #[allow(clippy::allow_attributes, clippy::arc_with_non_send_sync)] // For wasm
         let gl = std::sync::Arc::new(gl);
 
-        let painter = egui_glow::Painter::new(gl, shader_prefix, None, options.dithering)
-            .map_err(|err| format!("Error starting glow painter: {err}"))?;
+        let painter = egui_glow::Painter::new(
+            gl,
+            shader_prefix,
+            options.glow_options.shader_version,
+            options.dithering,
+        )
+        .map_err(|err| format!("Error starting glow painter: {err}"))?;
 
         Ok(Self {
             canvas,