Keep Tools/build/deepfreeze.py around (we may repurpose it for deepfreezing non-code objects),
and keep basic "clean" targets that remove the output of former deep-freeze activities,
to keep the build directories of current devs clean.
This ensures the source directory is not modified at build time, and different builds (e.g. different versions or GIL vs no-GIL) do not have conflicts.
Fix a race condition in "make regen-all". The deepfreeze.c source and
files generated by Argument Clinic are now generated or updated
before generating "global objects". Previously, some identifiers may
miss depending on the order in which these files were generated.
* "make regen-global-objects": Make sure that deepfreeze.c is
generated and up to date, and always run "make clinic".
* "make clinic" no longer runs generate_global_objects.py script.
* "make regen-deepfreeze" now only updates deepfreeze.c (C file).
It doesn't build deepfreeze.o (object) anymore.
* Remove misleading messages in "make regen-global-objects" and
"make clinic". They are now outdated, these commands are now
safe to use.
* Document generates files in Doc/using/configure.rst.
Co-authored-by: Erlend E. Aasland <erlend@python.org>