add menu entries and/or commands to toggle plugins

[teto]

Feature description

Kind of an openended issue.
My initial issue is that I contribute to several haskell packages, and haskell plugins like stan or hlint are noisy in the diagnostics.
To work around this:

1. One way to fix this is probably to ignore DEBUG/INFO diagnostics as a general diagnostic nvim functions. can be annoying if you want to keep hlint but not stan
2. add a hls.json with the correct config in every project. Can be annoying if you can't commit it.
3. change the config dynamically. This is the usecase I prefer, toggling on/off plugins at runtime .

Here is what I've tried:

M.toggle_stan = function ()
  local settings = M.generate_settings()

  settings.hls.default_settings.haskell.plugin.stan.globalOn = not settings.hls.default_settings.haskell.plugin.stan.globalOn
  return settings
end

M.restart_hls = function ()
 local new_settings = M.toggle_stan()
 vim.g.settings = new_settings
 vim.cmd [[ HlsRestart ]]
end

Seems to work. Looking at the HLS doc, it looks like it could be generalized, haskell-tools could parse the available plugins via --list-plugins and expose a :HlsTools plugin toggle/enable/disable <plugin>.

Unrelated/more of a general problem but I believe that a good way to expose commands could be to have a function that registers menu commands. For my own purpose I have created a local context menu where I add commands but maybe haskell-tools could have a

function register_menu_entries command (prefix)
   vim.cmd[[menu ]]..prefix..[[.Restart\ HLS  <cmd>HlsRestart<cr>]]
   ...
end

[mrcjkb]

This sounds like a good idea!
Not sure I fully understand the "registering menu commands" thing though.

I've been planning to rework the commands, so that it's less polluting and more similar to how I implemented it with rustaceanvim: One :Hls command (for haskell-language-server) and :Ht (for non-hls tools) with subcommands and completions, e.g. :Hls [re]start, :Hls stop, :Hls plugin toggle, and :Ht repl [...], etc (see #297)