Activate CDN for better storage speeds for non-US customers

On Azure side we prepared Azure FrontDoor, so we just need to add url changes in kernelci infrastructure to activate CDN (ex replace files.kernelci.org to cdn specific url for downloads in lava templates, for example).

Start by locating the KernelCI infrastructure configuration and LAVA templates that generate download URLs; confirm the prepared Azure Front Door CDN URL and identify the relevant non-US download references. Done means the intended downloads use the CDN while existing download behavior remains intact.

Written by the indexing model from the issue text.