Fix 3678 "problem parsing with statements"

[MeGaGiGaGon]

Description

This fixes #3678. The fix is done by adding two new functions to node.py, is_tuple_containing_star and is_generator, which are then added to the checks in maybe_make_parens_invisible_in_atom inside linegen.py, which is used by the function remove_with_parens that Jelle suggested modifying in a comment on #3678

Both functions are based on the existing is_tuple_containing_walrus. That makes me fairly confident in is_tuple_containing_star, since it does the same thing as is_tuple_containing_walrus, just with syms.namedexpr_test swapped for syms.star_expr. I'm less confident in is_generator since for a in b being called syms.old_comp_for seems weird and I don't totally understand syms/_python_symbols, but it seems to work.

Side note, _python_symbols is really hard to work with since node.type prints as an integer and the _python_symbol variable <--> integer relationship is done via setattr, so I ended up having to do [print(x, eval(f"syms.{x}") for x in dir(syms) if x[0:2] != "__"] to figure out what type generators get.

As usual, both names subject to bikeshedding. I chose is_tuple_containing_star because it compares with syms.star_expr, but is_tuple_containing_unpacking could also work. I chose is_generator since the issue is with a generator, though that could be something else since it doesn't match the syms.old_comp_for comparison.

The tests contain both a top level case and one where the issue is nested, since the nested case caused issues for me while making the fix.

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[JelleZijlstra]

Thanks!