Fix e2e external app test

[austin-denoble]

Problem

Test is currently failing in CI, but not locally. Need to investigate a bit from both ends.

Solution

• Move ts-external-app-test out of src/ to the top level of the repo.
• Improve some of the scripting in the external-app action and testing workflow - we were seeing failures even if the test itself was successful. Seemed like issues with grep'ing and trying to assert on things.
• Minor cleanup.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

workflow