In preparation of the upcoming 0.6.0 release I wanted to fix hls.
It introduces two new plugin packages, which are not on hackage yet.
I remove apply-refact overrides, because current apply-refact versions
are compatible with all ghcs we support, according to their changelog.
I override more of the hls dependencies globally on the whole package
set, to avoid a lot of duplicate compilations. And because @peti changed
my mind about this being a good practice.
hls now uses a released version of ghcide
We had a few "overrides" in configuration-common.nix that were really
extensions. They introduced packages that weren't in hackage-packages.nix.
The advantage of having a dedicated file for these packages is that we can still
place Nix-specific overrides to these packages in configuration-nix.nix. We
weren't able do this before because configuration-nix.nix extended only the
packages from hackage-packages.nix.
