Need the ability to unlink from a store and link to a new store via the Command Line

[filcap]

We are in the process of developing CLI scripts to automate certain tasks and we need to ensure that switching between Hydrogen environments is easy and seamless. Currently, we are facing an issue with the 'unlink' command, which is not fully detaching from the original store's connection and environment variables. To give you a better idea:

0. Assuming you already successfully established a connection/sync with npx shopify hydrogen link
1. run npx shopify hydrogen unlink
2. You do see a message confirming that you are successfully unlinked from the store
3. run npx shopify hydrogen link
4. You still only see storefronts that are within the same Shopify instance that you were previously connected to

I would expect that link would offer the ability to reconnect to a new instance so we can try to connect to new stores.

We suspect the reason for this is that in the .shopify/project.json even after unlinking the reference for the previous instance still exists in that file.

CC: @benjaminsehl