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 //ops
Change-Id: I00faeb969eaa70760a26256274925b07998c2351
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2915
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>