Design Preview can now switch templates

[kjohnson]

Description

This PR adds a new template form setting with a corresponding <SelectControl /> which switches the template used in the <DesignPreview /> canvas.

NOTE: There are some styling issues with the <select /> element that need to be addressed.

Visuals

Pre-review Checklist

• Acceptance criteria satisfied and marked in related issue
• Relevant @unreleased tags included in DocBlocks
• Includes unit tests
• Reviewed by the designer (if follows a design)
• Self Review of code and UX completed

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[jonwaldstein]

@kjohnson great job man! I did a hot fix for that select padding issue. Also, I left a reply and comments on this thread you started. Approving now so those can be addressed now or later.