fix(notifications): show correct Notification and Alert styling

[austingreendev]

Description

It looks like the .attrs() logic in styled-components has changed again styled-components/styled-components#2372

This was working after our 4.2.0 upgrade, but now certain props aren't being passed to their composed elements.

This is working in other packages as we only add to the className attribute.

Detail

To resolve this issue I removed all usages of styled(Well) and am now applying the required styles directly.

Checklist

• 👌 design updates are Garden Designer approved (add the
  designer as a reviewer)
• 💅 view component styling is based on a Garden CSS
  component
• 🌐 Styleguidist demo is up-to-date (yarn start)
• ⬅️ renders as expected with reversed (RTL) direction
• ♿ analyzed via axe and evaluated using VoiceOver
• 💂‍♂️ includes new unit tests
• 📝 tested in Chrome, Firefox, Safari, Edge, and IE11

[coveralls]

Coverage remained the same at 95.246% when pulling 4935232 on agreen/notifications-fix into 4a3b6a6 on master.