Enhancement: warn about repeated/shadowed names in function arg destructuring

[jafingerhut]

Example that would be nice to get a warning for, from @thheller on clojure-dev Slack channel:

(defn x [{:keys [foo]} foo]
  foo)
=> #'user/x
(x {} 1)
=> nil

The confusion is from foo being shadowed from a previous arg. Can be difficult to debug and understand what is going on.

[jafingerhut]

See this Clojure ticket for some potential related issues with map destructuring, although if Clojure 1.9 catches some of them as errors via clojure.spec, there is not much reason to repeat such checks in Eastwood.

https://dev.clojure.org/jira/browse/CLJ-1189

EDIT: It appears that the subtle mistakes mentioned in ticket CLJ-1189 are now caught as errors by Cloure 1.9.0