fix(form): update gap to use correct spacing 07, add v11 story

[tay1orjones]

Based on new guidance from design, spacing07 will be the recommended default spacing between form items/fields moving forward.

This PR updates the v11 form spacing examples using Stack to use gap={7} between fields.

Changelog

New

• added v11 story for FormGroup

Changed

• button: use intrinsic width by default (Closes [Bug]: Button has incorrect width when placed in Stack #10644)

Testing / Reviewing

• v11 storybook button stories should have no width regressions
• v11 storybook FormGroup story should have 32px/spacing-07 between fields
• v11 storybook FormGroup story button have a width relative to the content (intrinsic) width (not 100% width or the 20rem max-width as described in [Bug]: Button has incorrect width when placed in Stack #10644)
• v11 storybook Form story button should also have intrinsic width

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[laurenmrice]

Looks good to me ✅