Changes

Summary

1. Added tag Isabelle2023-RC0 for changeset f4221ae7544c
2. updated to zstd-jni-1.5.5-4;
3. updated to postgresql-42.6.0;
4. back to more concise build_release, thanks to build_host_macos = "mini3";
5. more PLATFORMS;
6. updated for release;
7. tuned NEWS;
8. more realistic factor;
9. proper trim_context;
10. proper exception positions;
11. proper trim_context / transfer, e.g. for Specification.definition;
12. tuned;
13. tuned;
14. tuned signature: more operations;
15. minor performance tuning: avoid append to end-of-list;