Use @shopify/dates formatDate function and memoize Intl.NumberFormat

[helloneele]

Description

Previous PRs: #1277, #1286

This makes use of the now exported formatDate function from the @shopify/dates package.

It also changes Intl.NumberFormat.format() to be memoized on SSR. This is because it is, same as Intl.DateTimeFormat.format(), leaking memory.

You can test this by doing node --inspect leak.js using node v10 or v12

// leak.js

setInterval(() => {
  var b;
  for (let i = 0; i < 100; i++) {
    b = new Intl.NumberFormat("ja-JP", {
      style: "currency",
      currency: "JPY"
    }).format(Math.floor(Math.random() * Math.floor(1000000)));
  }
}, 1);

Right after start

After a minute

I opened an issue in the node bug tracker to hopefully get the V8 fix backported to node v10/v12.

Type of change

• Patch: Bug/ Documentation fix (non-breaking change which fixes an issue or adds documentation)
• Minor: New feature (non-breaking change which adds functionality)
• Major: Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• I have added a changelog entry, prefixed by the type of change noted above

[michenly]

because we are using this at at least two places now, I think we should just add an enabledOnServer option to memoize. But that can also be done in a follow up PR.