"haskell-lsp" is deprecated in favour of "lsp"

[sjakobi]

We'll need to migrate dhall-lsp-server to the new package.

Some instructions on the migration can be found in the changelog for lsp-1.0.0.0: https://hackage.haskell.org/package/lsp-1.0.0.0/changelog

[sjakobi]

Regarding lsp-test: lsp-test >= 0.13 is based on lsp, so migrating to lsp should also help us become compatible with the latest lsp-test releases.