chore: test that autocapture allowlists are unioned

[pauldambra]

see this question in https://posthog.slack.com/archives/C02E3BKC78F/p1729035026457899

are the allowlist settings for autocapture unioned

i wasn't sure of the answer so let's add a test to show that they are

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated (UTC)
posthog-js	✅ Ready (Inspect)	Visit Preview	Oct 21, 2024 11:27am

[github-actions]

Size Change: 0 B

Total Size: 2.82 MB

ℹ️ View Unchanged

Filename	Size
dist/all-external-dependencies.js	172 kB
dist/array.full.es5.js	248 kB
dist/array.full.js	325 kB
dist/array.full.no-external.js	324 kB
dist/array.js	155 kB
dist/array.no-external.js	154 kB
dist/exception-autocapture.js	8.75 kB
dist/external-scripts-loader.js	2.19 kB
dist/main.js	156 kB
dist/module.full.js	325 kB
dist/module.full.no-external.js	324 kB
dist/module.js	155 kB
dist/module.no-external.js	154 kB
dist/recorder-v2.js	92.6 kB
dist/recorder.js	92.7 kB
dist/surveys-preview.js	56.7 kB
dist/surveys.js	62.1 kB
dist/tracing-headers.js	1.33 kB
dist/web-vitals.js	10.3 kB

_{compressed-size-action}

[pauldambra]

will merge this in without review since it's a test, but happy to revisit if folk spot something