In preparation for the solution of b/108, we need to consistently use
`depot.third_party` for packages that are only packed in the TVL depot
and `pkgs` for things that come from nixpkgs.
This commit cleans up a huge chunk of these uses in //fun
Change-Id: I45a7b392a9749fa7859ff5100dcea415bda807c3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2914
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>