ui_test: ensure all worker threads stay around

[RalfJung]

Also organize files such that the by far slowest test (weak_memory/consistency) always starts first. It still finishes last on my system... even after I halved the iteration count.

Fixes #2204

[oli-obk]

@bors r+

[bors]

📌 Commit 2891b55 has been approved by oli-obk

[bors]

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

1. git checkout ui_test_parallelism (switch to your branch)
2. git fetch upstream master (retrieve the latest master)
3. git rebase upstream/master -p (rebase on top of it)
4. Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
5. git push self ui_test_parallelism --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging ui_test/src/lib.rs
CONFLICT (rename/delete): tests/pass/weak_memory/consistency.stderr deleted in HEAD and renamed to tests/pass/0weak_memory_consistency.stderr in heads/homu-tmp. Version heads/homu-tmp of tests/pass/0weak_memory_consistency.stderr left in tree.
Automatic merge failed; fix conflicts and then commit the result.

[RalfJung]

@bors r=oli-obk

[bors]

📌 Commit c16c453 has been approved by oli-obk

[bors]

⌛ Testing commit c16c453 with merge e7507d6...

[bors]

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing e7507d6 to master...