[Feature] Expander improvements

[aappoalander]

Description

This PR introduces composition pattern for Expander.

• Expander content is now described using ExpanderTitle and ExpanderContent components that can contain ReactNodes.
• Expander groups can now contain ReactNodes in addition to expanders

In addition, multiple internal improvements are included:

• Components level implementation is removed
• AutoId is now used when generating id's automatically
• Aria support has been improved according to: https://www.w3.org/TR/wai-aria-practices-1.1/examples/accordion/accordion.html
• Focus indicators now use focus-visible
• Handling of children is now completely based on context rather than child manipulation

Related Issue

In addition multiple bugfixes are included:

• Content is no longer focusable/focused after closing an expander.
• Support for custom open/close all button is removed
• Aria attributes to support screen readers with open/close all button added
• Open/Close button stays in sync

Motivation and Context

Expander and ExpanderGroup implementation was no longer up-to-date with design specification and had quite a few issues. It was better to do a larger refactor rather than trying to address all issues with small fixes.

How Has This Been Tested?

Tested with TBA (CRA-TS, SSR, Styleguidist, DS-Site) using supported browsers and devices

Screenshots (if appropriate):

• No changes to visuals

Release notes

• Breaking changes: Complete API redesign and switch to content composition pattern. See [Feature] Expander improvements #414
  • Expander API
    • Removed: titleTag, title, titleProps, contentProps and internally used expanderGroup and index
    • Renamed: onClick => onOpenChange
    • Added: id
  • ExpanderGroup API
    • Static version Expander.group is no longer available. Use ExpanderGroup instead
    • Removed: onClickAll
    • Renamed: OpenAll => OpenAllText, CloseAll => CloseAllText
    • Added: AriaCloseAllText, AriaCloseAllText, toggleAllButtonProps, className

[ketsappi]

As the static version, Expander.group is no longer available because the API changes it might be good to mention that in release notes & PR description.