feat: support for spreading function bindings

[jackgdll]

Closes: #16086

Adds support for spreading function bindings using ... syntax.

Before:

<script>
  const [get, set] = bindLowerCase(value);
</script>
<input bind:value={get, set} />

After:

<script>
  function bindLowerCase(value) {
    return [
      () => value.toLowerCase(),
      (v) => value = v.toLowerCase()
    ];
  }
</script>
<input bind:value={...bindLowerCase(value)} />

Works with arrays [get, set] and objects {get, set}.
If either get or set is nullish it's a noop.
If either get or set is not a function a runtime error is thrown.

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.
• If this PR changes code within packages/svelte/src, add a changeset (npx changeset).

Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

🦋 Changeset detected

Latest commit: d4417cb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
svelte	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-16607-svelte.vercel.app/

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@16607