feat: make Go tools optional

[gabyx]

@domenkozar:

Here a small improvement on the nice Go language module:

• Make tools compiled with Go optional, for the user to choose what he needs.
  Not sure if the tools.packagesDefault is the right way to go, such that if tools.packages = null its defaulted to tools.packagesDefault

[domenkozar]

I like these changes, I need to think a bit more about the public interface since I'd like it to be universal across all langauges.

Something more like

{
  languages.X.dev.enable = false;
  languages.X.dev.packages.foo.enable = false;
  languages.X.dev.lsp.enable = true;
}

[gabyx]

jeah that would be nice.
so dev.packages beeing a submodule? Shall I try it? or do you wanna add a suggestion?

• How do tou handle package list which are defaulted to non-empty list, cause its additive merge behavior, not sure about the packagesDefault

[domenkozar]

@gabyx see #1974