Migrate to styled-system v5

[gesquinca]

Is your feature request related to a problem? Please describe. Migrate to styled-system v5.

Describe the solution you'd like We should migrate our components to use styled-system v5 to take advantage of new features like prop-types, style categories, and new Custom Styles api.

Describe alternatives you've considered Staying in v4.

Additional context https://styled-system.com/guides/migrating

Acceptance criteria:

• should have styled-system v5 branch
• should upgrade any api changes to components
• should write down any documentation changes that are needed
• verify no components broke
• verify all component styles still work
• should accept all styled-system v5 props E: 1D

[gesquinca]

• [ ] remove CONSTANTS file in favor of style categories. https://styled-system.com/guides/migrating#style-categories
• [ ] make sure key foundation components are working correctly: Box, Flex,
• [ ] make sure typographic components are working correctly: Text, Heading
• [ ] make sure form/input components are working correctly: Input, Button
• [ ] update default theme to comply with theme specification https://styled-system.com/theme-specification