haskell-language-server

* Invert the dependency between ghcide and hls-plugin-api

This PR includes changes both to ghcide and HLS to implement the reorg described in https://github.com/haskell/ghcide/issues/936#issuecomment-751437853

To summarise:

- `hls-plugin-api` no longer depends on ghcide.
- `ghcide` now depends on `hls-plugin-api` and exposes:
  - The ghcide HLS plugin
  - The `asGhcIdePlugin` adaptor

The goals are:
- to be able to break the `ghcide` HLS plugin down
- to rewrite exe:ghcide on top of the HLS plugin model.

The ghcide side is reviewed in https://github.com/haskell/ghcide/pull/963

If this change is accepted there are two further considerations:
- This would be a good moment to merge the 2 repos, so that there is no history loss.
- `hls-plugin-api` will need to be released to Hackage prior to merging https://github.com/haskell/ghcide/pull/963

* clean up

* Fix the ghcide plugin to include the rules

* clean up PartialHandlers definition

The ghcide partial handlers for completions, code actions and hover are not
really being used, since they get overriden by the `<> ps` append. This is due
to the right-biased semantics of `PartialHandlers`

* Move ghcide LspConfig into Ide.Plugin.Config

* Use HLS plugins in ghcide

For now there is only one, the main ghcide plugin. But this will allow us to
break it down in more fine grained plugins with parallel semantics, both for
execution and error handling

* Fix hlints

* Revert "Temporarily disable the upstream branch for benchmarks"

This reverts commit 7bb3c6ef.

* Disable the Windows 8.6.4 test

* Fix unrelated hlints

Not sure why these are triggering now.

Linting should be restricted to the Diff ...