stepper: add breakpoint navigation

[wkc75]

Authors

Wong Kin Chong, wongkinchong75@gmail.com
Raaghul, Raaghulk04@gmail.com

Description

• derive substitution-stepper breakpoint steps from editor breakpoints
• make the double-chevron controls jump to previous and next breakpoint steps

Type of change

• New feature (non-breaking change which adds functionality)

How to test

1. Open the playground and switch to the substitution stepper.
2. Enter a Source program with multiple reducible steps on different lines.
3. Set breakpoints on a few of those lines in the editor gutter.
4. Run the program.
5. In the substitution visualizer, use the double-chevron-left and double-chevron-right buttons.
6. Verify that the controls jump to the previous and next breakpoint-related step instead of only moving to the first or last step.
7. Verify that normal single-step navigation still works as expected.

Checklist

• I have tested this code
• I have updated the documentation