fix(avatars,modals,notifications): prevent dev console warnings

[jzempel]

Description

This gets warnings out of the dev console for:

• rendered Avatar components that are legitimately hidden
• Modal.Close components that are described by a a tooltip
• leaked styled toast notification placement prop

Checklist

• 👌 design updates will be Garden Designer approved (add the designer as a reviewer)
• 🌐 demo is up-to-date (npm start)
• ⬅️ renders as expected with reversed (RTL) direction
• ⚫ renders as expected in dark mode
• 🤘 renders as expected with Bedrock CSS (?bedrock)
• 💂‍♂️ includes new unit tests. Maintain existing coverage (always >= 96%)
• ♿ tested for WCAG 2.1 AA accessibility compliance
• 📝 tested in Chrome, Firefox, Safari, and Edge