[PATCH 0/7] libstdc++: Use gdb.ValuePrinter in pretty-printers

[Tom Tromey]

GDB 14 will include a gdb.ValuePrinter tag class that can be used by
pretty-printers to signal they will accept any extensions that GDB
happens to make over time.

This series started as an attempt to change the libstdc++ printers to
support this.  This just involves renaming a bunch of attributes.
There aren't many interesting GDB API additions yet (and I didn't
implement the new ones in libstdc++ yet anyway), but seeing as these
are the flagship pretty-printers, it seemed worthwhile to do.

I added patch 1 when debugging the changes; then proceeded to fix a
bunch of small issues that were pointed out by flake8.

Tested on x86-64 Fedora 36.  Let me know what you think.

Tom