**Summary** Add a formatter progress testing script to CI. This script
will 1) print the black compability on each run 2) catch regressions wrt
to formatter stability, emitting invalid syntax and other kinds of bugs
(e.g. #5917) before they land on main 3) have an additional layer of
real world tests when implementing new nodes or other new formatter
code.
This is currently a bash script, i'm not sure if we want to keep it that
way, or switch to e.g. the regular ecosystem scripts. The output
separation of `format_dev` could also use some polishing. We should also
consider pinning commits so we don't get spurious regression when they
change their code.
**Test Plan** The script extends CI.
