fix: expose the last activity timestamp in session id check result

[pauldambra]

When you check the session id in posthog you get a bunch of useful information but not the last activity timestamp.

While working on an example of solving a problem in https://posthog.com/questions/post-to-slack-on-new-replay-in-playlist I had to reach into persistence manually to make it work.

Let's expose the useful information, since it's useful

[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 23, 2024 2:34pm

[github-actions]

Size Change: +240 B (+0.01%)

Total Size: 2.89 MB

Filename	Size	Change
dist/array.full.es5.js	248 kB	+24 B (+0.01%)
dist/array.full.js	334 kB	+24 B (+0.01%)
dist/array.full.no-external.js	333 kB	+24 B (+0.01%)
dist/array.js	155 kB	+24 B (+0.02%)
dist/array.no-external.js	154 kB	+24 B (+0.02%)
dist/main.js	156 kB	+24 B (+0.02%)
dist/module.full.js	334 kB	+24 B (+0.01%)
dist/module.full.no-external.js	333 kB	+24 B (+0.01%)
dist/module.js	155 kB	+24 B (+0.02%)
dist/module.no-external.js	154 kB	+24 B (+0.02%)

ℹ️ View Unchanged

Filename	Size
dist/all-external-dependencies.js	182 kB
dist/exception-autocapture.js	8.75 kB
dist/external-scripts-loader.js	2.19 kB
dist/recorder-v2.js	102 kB
dist/recorder.js	103 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}