Don't set up lspconfig clients if conflicting plugins are installed

[mrcjkb]

Is your feature request related to a problem? Please describe.

Hey 👋

I sometimes have users opening issues/discussions because mason-lspconfig sets up lspconfig configurations that conflict with my plugins (haskell-tools.nvim, rustaceanvim), when they use mason to install a language server.

Often (usually when using a distro), they aren't aware that mason-lspconfig is installed.

Describe the solution you'd like

Would it be feasible for mason-lspconfig.nvim to check for the presence of certain plugins (e.g. by searching the runtimepath or with a pcall('require', ...)), and basing the default behaviour on the presence of those plugins?

Describe potential alternatives you've considered

N/A

Additional context

Example: mrcjkb/rustaceanvim#94

[mrcjkb]

After looking at the codebase, it looks to me like mason-lspconfig doesn't actually call the lspconfig configurations' setup functions automatically (@williamboman can you confirm this?).

I believe it's distros like LazyVim and AstroNVim that are adding this behaviour.