Fix type annotations the linter found to be wrong

Async ids come from `get_function_name`, which returns a string, but
were documented as numbers.

`setmetatable` in clusterio's compat module loses `LibCompat` on the
module return, so the require is cast.

`GuiData.__index` accepts a `DataKey` but emmylua needs that as an
index signature on the class.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

exp_groups/module/control.lua

@@ -3,7 +3,7 @@ Adds permission group syncing to clusterio
 ]]
 
 local clusterio_api = require("modules/clusterio/api")
-local compat = require("modules/clusterio/compat")
+local compat = require("modules/clusterio/compat") --[[@as LibCompat]]
 
 --- Top level module table, contains event handlers and public methods
 --- @class ExpGroups