Changes

Summary

1. back to post-release mode -- after fork point;
2. Added tag Isabelle2023-RC3 for changeset f5fb5bb2533f
3. clarified option name (see also ff43a524aa5d);
4. more thorough ML_Heap.restore: include ancestors; prefer simultaneous ML_Heap.get_entries: just one database access for heap hierarchy;
5. more robust: atomic file-system result via tmp file;
6. removed junk (amending 8cd399b25dac);
7. more robust wrt. undefined state;
8. more informative error;
9. more robust;
10. tuned signature;
11. clarified signature: more explicit types;
12. more informative shasum: show differences explicitly;
13. tuned messages;
14. more robust ancestor_results: avoid total existence failure after build_process has crashed elsewhere;
15. clarified synchronized regions: avoid deadlock of Build_Cluster operations on other thread vs. return_code(), notably via capture() error handling;