Add better support for Haskell stack compiler tools (#1851)

* Add better support for Haskell stack compiler tools

This commit adds support for `stack` as the executable of a tool. This
follows a pattern that has been implemented for `bundler`'s tool chain.

* Move hlint command to linter file
* Add vader test for stack exec handling
* Update ghc-mod to support stack execution

`ghc-mod` was previously broken into 2 linters.

1. ghc_mod
2. stack_ghc_mod

This additional linter is not necessary with proper support for
executable variables and `stack exec` handling.

* Support stack exec in hfmt
* Support stack in hdevtools

autoload/ale/fixers/brittany.vim

@@ -3,11 +3,17 @@
 
 call ale#Set('haskell_brittany_executable', 'brittany')
 
-function! ale#fixers#brittany#Fix(buffer) abort
+function! ale#fixers#brittany#GetExecutable(buffer) abort
     let l:executable = ale#Var(a:buffer, 'haskell_brittany_executable')
 
+    return ale#handlers#haskell_stack#EscapeExecutable(l:executable, 'brittany')
+endfunction
+
+function! ale#fixers#brittany#Fix(buffer) abort
+    let l:executable = ale#fixers#brittany#GetExecutable(a:buffer)
+
     return {
-    \   'command': ale#Escape(l:executable)
+    \   'command': l:executable
     \       . ' --write-mode inplace'
     \       . ' %t',
     \   'read_temporary_file': 1,