[dev]: add check to e2e tests for connection

[jsjoeio]

Problem

We've noticed the occasional timeout in e2e tests. In an effort to reduce flakiness due to connection timeouts, we think it would be beneficial to add a check for the connection.

Solution

Add method to CodeServer e2e model to check connection by asserting that the CODE_SERVER_ADDRESS shows up in the bottom left-corner. If it doesn't, reload.