basesdk: Fix overlay inclusion by splitting it up

The basesdk overlay was not actually included since debos was not following the symlink to the sdk one.

Avoid the symlink by getting rid for the sdk recipe of the $arch-$type mechanism, which is an ancient relic inherited from the conversion from the old cb_build pipeline.

Splitting the overlay into semantic units also allow us to avoid the Eclipse icon on the base SDK desktop, where Eclipse is not installed.