incorporate latest upstream changes

What does this MR do?

As there are quite some fixes and optimisations in the upstream version, not yet incorporated, I thought that it might be time for a new release to profit from the upstream improvements. (@camilstaps If you think differently about this, we can also delay the release, but still merge the changes as "unreleased".)

I could just merge the changes without resolving any conflicts. I could furthermore run all iTasks CI tests with this version, to verify that everything still works.

I omitted all refactorings and preparations for future changes from the changelog. I also don't mentions fixes of the "lazy tuple recursion optimisation", as this is only added with this MR.

Changes to public APIs

The -oltr flag is added.

Author's checklist (required)

• If bugs have been solved, tests have been added (guidelines)
• A changelog entry has been added (guidelines)
• Newly added code is documented (guidelines)
• Newly added code has a style consistent with the rest of the repository
• Intermediate commits compile (use git rebase -i main if not)

Related issues