Refactor: update base styles to support custom fields

[jonwaldstein]

Description

This updates the base form design styles to utilize css grid with gap to account for spacing of custom fields.

This was most noticeable on multistep form with some fields using margin and others using gap. So using grid by default gives even spacing between fields and allows custom form designs to further customize.

Affects

The base form design styles

Visuals

Before

After

Testing Instructions

• Pull branch and run npm run dev
• Add some custom fields and switch between form designs
• Make sure the spacing looks acceptable.

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

[jonwaldstein]

@pauloiankoski small one, ready for review.

[pauloiankoski]

Looks good!