Better error reporting: Page errors and per test timeouts

Currently, the most common Testee error is test timeouts. This can happen for any reason. Some solutions for implementing better reporting:
- [ ] Report errors on the page (potentially with a global error handler) like syntax errors etc
- [ ] Implement a per-test timeout. Currently a timeout does not include if it timed out on a specific test.

Start by tracing the existing timeout handling and browser page error reporting paths, since the issue names no files or tests. Review how failures are currently surfaced, then verify that page errors are reported and that timeout messages identify the specific test that exceeded its limit.

Written by the indexing model from the issue text.