Improve e2e tests

[MexicanAce]

Problem

Updating e2e tests is cumbersome and there are ways to make our lives easier/automated (especially if you're just touching the smart contracts), so here's the list:

• Update gateway's contract addresses within packages/gateway/stores/client.ts for InMemoryNode to pull from .env file
• Add a command to easily populate this .env file
• Present better errors when tests fail because of Contract issues (e.g. Capture front-end console errors for both the demo-app and the gateway)
• Reduce the time to run browser installations to speed up CI
• Make it a single command to run the entire e2e test suite (that starts the InMemoryNode for you)