gh-157244: Fix potential division by zero in turtle.py

[evdakim1234]

Fixes #157244

This PR adds guard clauses to prevent potential ZeroDivisionError exceptions in the turtle module:

-Validates xspan and yspan in setworldcoordinates to prevent division by zero during coordinate scaling.
-Validates steps in circle before using it as a denominator.
(Backport request: to 3.13).

• Issue: Potencial division by zero in turtle.py #157244

[python-cla-bot]

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[aisk]

I'm not sure changing the DevideByZero to ValueError is the right solution and meaningful, but if we decided to merge this, a test and a news entry is required.

[encukou]

No, replacing ZeroDivisionError by ValueError is not meaningful.