Changes

Summary

1. tuned GUI, notably for scalable FlatLaf;
2. clarified default L&F;
3. support for additional look-and-feels;
4. avoid rescaled fonts, e.g. dockable buttons on Windows L&F after opening a new view;
5. some algebra material for HOL: characteristic of a ring, algebraic integers
6. HOL-Data_Structures: added Selection and time functions for list functions
7. merged
8. discontinued body_range (again): does not quite work, because Position.thread_data is plain Toplevel.pos_of only;
9. clarified: command keyword position is sufficient (amending 693a39f2cddc);
10. ignore error messages produced by CVC4 when generating BV
11. One useful lemma/simprule
12. isabelle update_cartouches;
13. tuned --- prefer explicit position;
14. recovered body_range from eca176f773e0 --- its Command.core_range is in conflict with batch-build markup;
15. tuned;
16. support more command positions, analogous to Command.core_range in Isabelle/Scala;
17. tuned;
18. more uniform core_range (amending def3ec9cdb7e);