[Quick Add Bulk] - Clean up network requests

[sofiamatulis]

Describe the enhancement you'd like

Quick Add Bulk - Clean up network requests to improve performance:

https://screenshot.click/05-16-6bol4-qljje.mp4

Let's cache the modals

[sofiamatulis]

1. intersection observer to load the modal html
2. cache the data in JS (like filters https://github.com/Shopify/dawn/blob/main/assets/facets.js#L269)
3. update cache when items are added to cart in the modal
4. have pubsub listening to changes and updating cache as needed
5. clear cache when navigating away from the page (will already happen since im saving it like filters in a var)
6. note: promise may be needed in case of buyer opening the modal fast + adding items to cart in the modal