Update libddwaf to 1.6.2

[CarlesDD]

What does this PR do?

Updates libddwaf to 1.6.2 Turn all scalars in objects passed to ddwaf_run to strings

Motivation

Additional Notes

Closes #69

Describe how to test your changes

Checklist

• [ ] The CHANGELOG.md has been updated
• [ ] Unit tests have been updated and pass
• [ ] If known, an appropriate milestone has been selected

[simon-id]

did you end up supporting bigints when coerce to string is true btw?