dns-prefetch s.w.org conditionally via javascript

[superpoincare]

For many users, dns-prefetch to s.w.org is not needed if they aren't using Jetpack or any plugin which connects to it. It's because:

1. A page may not have an emoji
2. Even if the page has it, the browser may support emojis. Going forward the support will increase.

Hence I propose the dns-prefetch to s.w.org be made only if the feature detection detects wp-emoji-release needs to be loaded or if possible page needs an emoji svg.

[Presskopp]

Related: #40426

[garrett-eclipse]

Related - #44001
*If emoji scripts gets internalized due to privacy concerns then the need to prefetch s.w.org will be gone.