chore: test component exports + async (#17241)

Regression-test, this works already. Closes #16657

packages/svelte/tests/runtime-runes/samples/async-component-exports/Child.svelte

@@ -0,0 +1,9 @@
+<script>
+	export function foo() {
+		console.log('foo');
+	}
+
+	const value = await Promise.resolve('bar');
+
+	export const bar = () => console.log(value);
+</script>

packages/svelte/tests/runtime-runes/samples/async-component-exports/_config.js

@@ -0,0 +1,12 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target, logs }) {
+		await tick();
+		const [log] = target.querySelectorAll('button');
+
+		log.click();
+		assert.deepEqual(logs, ['foo', 'bar']);
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-component-exports/main.svelte

@@ -0,0 +1,11 @@
+<script>
+	import Child from './Child.svelte';
+
+	let child;
+</script>
+
+<Child bind:this={child} />
+<button onclick={() => {
+	child.foo();
+	child.bar();
+}}>log</button>