Fix pass-through-help on vector aliases by merging meta on aliases

This fixes pass-through-help when used on vector valued aliases. Ex:

```clojure
:aliases {"a" ^:pass-through-help ["run" "-m" "some.core"]
          "b" ^:any-meta ["a"]}
```
The meta on task b will be `{:pass-through-help true, :any-meta true}`.