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 //third_party
Change-Id: Ic382c0cdea7330a84d5f0b7d109c824ddceb94e7
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2912
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>