Bug fixes

Fixing duplicates occured at multiple image select.

Revoked Drupal 9 support as it caused more problems than it solved. No reason to run this on Drupal 9 anyway as it would not detect most of the deprecated APIs either way. Now explicitly impossible to do so. Also, more resiliency around PHPStan failures!

• Added support for Drupal 9

This release fixes the issues:
#3171741: Context module: "Menu Reactions" will not work because menu.active_trail has a different menu service provider.

This release contains a security fix.

• Issue #3170658: Upgraded [Bootstrap Barrio] base theme from ~4.0 to ~5.0
• Issue #3171962: Updated RFS from ~8.0 to ~9.0 for Vartheme BS4 and VARTHEME_BS4_SUBTHEME
• Issue #3170682: Converted to use REM and EM instead of PX