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/native/glow_integration.rs

@@ -184,7 +184,7 @@ impl<'app> GlowWinitApp<'app> {
         let painter = egui_glow::Painter::new(
             gl,
             "",
-            native_options.shader_version,
+            native_options.glow_options.shader_version,
             native_options.dithering,
         )?;
 
@@ -952,12 +952,12 @@ impl GlutinWindowContext {
 
         use glutin::prelude::*;
         // convert native options to glutin options
-        let hardware_acceleration = match native_options.hardware_acceleration {
-            crate::HardwareAcceleration::Required => Some(true),
-            crate::HardwareAcceleration::Preferred => None,
-            crate::HardwareAcceleration::Off => Some(false),
+        let hardware_acceleration = match native_options.glow_options.hardware_acceleration {
+            egui_glow::HardwareAcceleration::Required => Some(true),
+            egui_glow::HardwareAcceleration::Preferred => None,
+            egui_glow::HardwareAcceleration::Off => Some(false),
         };
-        let swap_interval = if native_options.vsync {
+        let swap_interval = if native_options.glow_options.vsync {
             glutin::surface::SwapInterval::Wait(NonZeroU32::MIN)
         } else {
             glutin::surface::SwapInterval::DontWait