Move the `let in` block defining `displayName` and `packageName` up so
it doesn't have to deal with the module arg `name` shadowing `args.name`.
This simplifies the implementation and reduces repetition.
The default for `lsp.servers.<name>.activate` used to be conditional on
whether `name == "*"`. This is leftover from before the * server was
moved to its own `global-server.nix` module and can now be removed.
Adds two internal per-server options: `packages.prefix` & `packages.suffix`.
These options allow the server module to install multiple packages, and
control which end up being prefixed or suffixed on the PATH.
This simplifies the propagating code in `modules/lsp/servers/default.nix`,
which can now zip up the enabled server `packages` attrs.
Adding a module in the following places will import the module into that
specific server's submodule.
This allows creating server-specific options.
Added a test case to ensure all custom modules correspond to an actual
server option to avoid accidental dead code.
