fix: resolve deprecation warnings in example test runs

[sheremet-va]

Running pnpm test printed deprecation warnings in 6 of 7 examples, mostly from plugins predating Vite 8 / Rolldown.

• preact/react/svelte: bump @preact/preset-vite, @vitejs/plugin-react, @sveltejs/vite-plugin-svelte to Rolldown-aware versions (drops deprecated esbuild/optimizeDeps.esbuildOptions warnings)
• qwik: bump to 1.20 (fixes wasm init warning) and set oxc: false, the Rolldown equivalent of the esbuild: false the plugin sets
• solid: replace deprecated solid-testing-library with @solidjs/testing-library and pass a component function to render() (fixes createRoot warning)
• vanilla: remove leftover debug import of deprecated vitest/suite

pnpm test now runs warning-free, all 7 suites pass.