Foundation: Update standard template naming

[bheston]

Pull Request

📖 Description

As part of the next major release of fast-foundation, we wanted to do a complete review of the component templates and align the structure and naming as much as possible.

This PR unifies the naming and cleans up some test styles, especially around the recent update to the start and end slots.

Before on the left, update on the right. "C" = class, "P" = part, "R" = role, "S" = slot. 💔 = potentially style-breaking.

Dialog

• 💔 Flatten "positioning-region" element to host

Radio group

• 💔 Rename “positioning-region” to “control”
• 💔 Remove “horizontal” or “vertical” class, use attribute on host instead

Tab

• Wrap default slot in “content”

Toolbar

• 💔 Rename “positioning-region” to “control”

👩‍💻 Reviewer Notes

Review the Storybook site, or the illustrations of the components before and after, compared to the changes in code.

📑 Test Plan

Tested via comparison against proposal and in Storybook.

✅ 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

[janechu]

Closing this as it seems like these changes will break user styling downstream.