Add HarnessBuilder::with_render_options() (closes #7630) (#8060)

Allows to override the default `PREDICTABLE` render options, e.g. if
it's desired to create snapshots with the exact texture options used by
the app.

See #7630 for details / examples.

crates/egui_kittest/src/lib.rs

@@ -116,6 +116,11 @@ impl<'a, State> Harness<'a, State> {
 
             #[cfg(feature = "snapshot")]
             default_snapshot_options,
+
+            // rustfmt adds this weird indentation below.
+            // See: https://github.com/rust-lang/rustfmt/issues/5920
+            #[cfg(feature = "wgpu")]
+                render_options: _,
         } = builder;
         let ctx = ctx.unwrap_or_default();
         ctx.set_theme(theme);