codefix: Fix code actions that return Command[] directly instead of CodeAction[] (#3929)

According to
https://microsoft.github.io/language-server-protocol/specifications/specification-3-17/#textDocument_codeAction,
the response to textDocument/codeAction is:

    (Command | CodeAction)[] | null

and the code only handled the case where it was a CodeAction that either
specified an edit or a command, but didn't handle a direct Command.

Note that the specification also says that both can be specified and
then the edit is applied first, then the command. Furthermore, there
seems to be some hacky code handling arguments directly, which I suspect
is non-standard and only works with a specific LSP server that happens
to pass the edits in the arguments unmodified.

autoload/ale/codefix.vim

@@ -201,6 +201,14 @@ function! ale#codefix#ApplyLSPCodeAction(data, item) abort
         \   l:command.arguments,
         \)
 
+        let l:request_id = ale#lsp#Send(a:data.connection_id, l:message)
+    elseif has_key(a:item, 'command') && has_key(a:item, 'arguments')
+    \&& type(a:item.command) == v:t_string
+        let l:message = ale#lsp#message#ExecuteCommand(
+        \   a:item.command,
+        \   a:item.arguments,
+        \)
+
         let l:request_id = ale#lsp#Send(a:data.connection_id, l:message)
     elseif has_key(a:item, 'edit') || has_key(a:item, 'arguments')
         if has_key(a:item, 'edit')