fix: rework data-grid scroll into view

[scomea]

📖 Description

Data-grid only invoked scroll into view when it was the scroll container itself and not as a variable height container that was taller than the page. This change updates scroll-into-view behavior and keyboard page up/down behavior to handle all cases.

This changes the api of FASTDataGrid by adding a "page-size" attribute that allows authors to control how many items to jump over during page up/down operations. If unset the grid uses either it's own height/grid row height or document height/grid row height depending on whether the grid itself is a scrolling container or not.

🎫 Issues

closes https://github.com/microsoft/fast/issues/6119

📑 Test Plan

Hoping to add playwright tests when that is available

✅ Checklist

General

• [x] I have included a change request file using $ yarn change
• [ ] I have added tests for my changes.
• [x] I have tested my changes.
• [x] 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

⏭ Next Steps