Migration: Add correct type for bind:this of Components when using the migration script

[FoHoOV]

Describe the problem

In svelte 4 when typing the bind:this we used this:

<script lang="ts">
	import Component from "./Component.svelte";

	let comp: Component | undefined = undefined;

	onMount(()=>{
		comp.sayHi();
	})
</script>

<Component bind:this={comp} />

After running the migration script nothing changes whilst it should be:

<script lang="ts">
	import Component from "./Component.svelte";
	import {onMount} from "svelte";

	let comp: ReturnType<typeof Component> = undefined;

	onMount(()=>{
		comp.sayHi();
	})
</script>

<Component bind:this={comp} />

Describe the proposed solution

Use ReturnType<typeof X> or use the utility type in #13441 which makes bind:this type forward-compatibale - easier to change internally without requiring change on the comsumer code.

here is the REPL

Importance

would make my life easier