slick 8.x-1.0-beta2

A couple of fixes and integration issues.

• Removed redundant Preloader option since the classes are within image containers. Maybe more reasonable for Views later which can text, images, etc.
• Fixed for broken dots.
• Update arrows defaults values.
• Updated slick.load.min.js to v1.6.0.
• Updated JS to Blazy JS v1.6.0 as per #2716765: Map or rework breakpoints into srcset as per v1.6.0.
• Added option Preloader for Slick > 1.5.9 which is unfortunately still broken.
• Removed _slick_build_slide() to reduce function calls.
• Removed expensive SlickManager::getAvailableSkins().
• More cleanups.
• A couple of cleanups.
• #2710221 by xanterax: Fatal error by colliding constructor traits.