Prevent session garbage collection during functional tests

1. Changes in the MR are small, clear, and do what the title and summary say they should. No complaints, not even nits. And I'm usually good for at least something pedantic to point out during a review. 😂
2. CI pipeline is all green.
3. The fact that we might have random garbage collection during tests is definitely a source of instabilityts.
4. This random query behavior has been causing trouble in the performance tests and other spots.

Therefore, RTBC.

Thanks!
-Derek

p.s. Out of scope, but I'll say it anyway. Expanding the full context for the MR changes, I notice this (untouched by the MR):

      // @todo Decide in https://www.drupal.org/project/drupal/issues/3395099 when/how to trigger deprecation errors or even failures for contrib modules.

But 📌 Follow-up for #3361534: config validation errors in contrib modules should not cause deprecation notices, unless they opt in Active is Closed (fixed). Do we need a followup to remove that @todo?

Looks good to me too. The way it's implemented makes a lot of sense to me.

It will only work for browser tests, but I can't immediately think of a scenario where we would worry about session gc during kernel tests.

The file copy is now unnecessary - we can read it and then write the file.

Feel free to set back to RTBC if this is sufficient.

Oh I briefly thought about doing this when working on the MR then immediately forgot about it again. Makes sense to me. I think this is straightforward enough I can re-RTBC.

Committed and pushed 4c8f1df76b to 11.x and 9f0c3d9fce to 10.3.x. Thanks!

Great eyes, as always, @alexpott! Sorry I missed that. 😅

Nice work, everyone! 🙏 Thanks!

Automatically closed - issue fixed for 2 weeks with no activity.