Drop node12 support

[Kikobeats]

We are supporting node12 essentially because it's the minimum Node.js version supported by Next.js.

The moment that changes, we can:

• [ ] Upgrade jest@28 to jest@29
• [ ] Update esbuild target to the new target
• [ ] Remove node12 from docs
• [ ] Remove uuid polyfill
• [ ] Remove http missing methods.
• [ ] Remove util missing methods.
• [ ] Remove buffer <-> blob patch.
• [ ] Remove AbortSignal workaround for Jest.

[styfle]

Let's go ahead and ship this now that Next.js just landed:

• https://github.com/vercel/next.js/pull/41150