- Added micro-optimization for BlazyStyleBaseTrait::getFirstImage.
- Opened supports for Responsive image for GridStack since the removal of custom
  breakpoints at blazy:2.0.
- Cleaned up few more TODOs.
- Removed no longer relevant D8.7 traces.
- Disabled BlazymanagerBase::buildSkins for sub-module own skin implementations.
- Moved Blazymanager::setAttachments into BlazymanagerBase::setAttachments to
  re-use for sub-modules.
- Moved BlazymanagerBase::isCrop into BlazyFormatter::isCrop due to being usable
  only at formatter level, not Views, etc.