Support stable `remotePattern` option

The `remotePatterns` option is going to be promoted to stable, and so [will no longer be in the `experimental` object](https://github.com/vercel/next.js/commit/4cc7f11da2194aa9ffce4e04b8a0c6ee340f4f85#diff-a9aa71ef3757abaca165c8b1b8726b6d3aca8f95c9db3f12ac9176aadfd0c7f8L400) so we need to support both.