Update button styles, and update variant types in application components

[scottqueen-bixal]

PR Summary

This works to update our buttons for unstyled, secondary, default, and outline, it also updates the respective type to the associated location on the application as recommended by USAGov.

Related Github Issue

• Fixes DESIGN | Update Button styles #1446

Detailed Testing steps

• pull changes locally
• cd benefit-finder
• npm install

• npm run dev:storybook
• navigate to http://localhost:6006/?path=/docs/shared-components-button--docs
• confirm the Button variant styles are as follows

• tab to focus, confirm variant styles are as follows

• npm run start
• ensure the following variant assignments have taken place in the application
• start button is secondary

- [ ] grouped buttons in navigation of form steps are `outline` for `back`, and `secondary` for `continue` - [ ] modal buttons are `secondary` - [ ] results view toggle to `not eligible` lists are `secondary` - [ ] accordion links as buttons inside the accordion content are `secondary` - [ ] `share` and `email` buttons are replaced with "trigger" anchor elements

[gchi25]

Need to update the testing instruction.

[gchi25]

Tested. Worked as expected.