fix: port anchored region viewport lock fixes

[scomea]

Pull Request

📖 Description

This change ports changes from https://github.com/microsoft/fast/pull/6260 to the archived version

🎫 Issues

https://github.com/microsoft/fast/issues/6125

👩‍💻 Reviewer Notes

This does not include minor styling changes that prevent some z-index issues when menus overlap and give menus fancy "size to viewport" behavior.

📑 Test Plan

These changes are currently untested, we need some way to vet before checkin.

✅ Checklist

General

• [x] I have included a change request file using $ yarn change
• [ ] I have added tests for my changes.
• [ ] I have tested my changes.
• [ ] I have updated the project documentation to reflect my changes.
• [ x] I have read the CONTRIBUTING documentation and followed the standards for this project.

Component-specific

• [ ] I have added a new component
• [x] I have modified an existing component
• [ ] I have updated the definition file
• [ ] I have updated the configuration file