TMP: Try running E2E tests against the wp.com environment - #57342

What?

This temporary PoC is for running core E2E tests against the wordpress.com environment. It's not intended ever to be merged.

Testing Instructions

1. Define the following env variables (ping me for the values if you're an A11n):

   export WP_USERNAME=?
   export WP_PASSWORD=?
   export WP_BASE_URL=?
   export WP_CLIENT_ID=?
   export WP_CLIENT_SECRET=?

2. Run npm run dev

3. Run npm run test:e2e:playwright -- --headed to run all tests.
   Append suite name (e.g. rich-text.spec.js) to run only that.

cc: @fullofcaffeine @noahtallen @tyxla @griffbrad