gh-153171: Produce specialized syntax errors for 'not' after an operator in more...

gh-153171: Produce specialized syntax errors for 'not' after an operator in more positions (GH-153175)

Move the invalid_factor rule from term to factor and the
invalid_arithmetic rule from shift_expr to sum, so that they are
tried at all positions where the invalid construct can occur.
Previously a generic "invalid syntax" error was reported for
constructs like "1 << 2 + not x" or "1 * + not x".

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>