Reduce the number of GitHub fetches when rebuilding the local addon cache by using a remote cache stored on FreeCAD's servers.
Intended to mitigate the Addon Manager hitting GitHub's rate limiters.
Addresses, but does not fully close, #15059
* Addon Manager: Refactor primary view and enable composite
This brings back something akin to the original Addon Manager display, with the side-by-side display of the list and details views.
