Add optional `if break:` suite to `for/while`

Ideas
20

I have done use-case analysis for this as part of:

  1. Generalize `elif-else` to all compound statements
  2. `while-elif-else`, `for-elif-else`, `try-except-elif-else`

Cpython repo with site-packages from .venv.

  1. try-else-if - 407
  2. for-else-if - 114
  3. while-else-if - 28

Those are with else immediately followed by if (my proposal was adding conditional-like-elif). Thus, numbers for pure else would be much higher.

I do not use while/for-else very much, but when I do, I always feel that something is missing.