Preserve reader meta of fn

[borkdude]

(meta ^:foo (fn []))

should return {:foo true} but currently returns nil.

One problem here is that we should get rid of the edamame location metadata and only add metadata to the function if there was any non-location metadata.

TODO:

• fix location in exception for (defn foo []) (foo 1)
• a nasty side effect of putting the location metadata in a sub-key:

$ clojure -M:babashka/dev '(defmacro foo [m] (prn (meta m))) (foo (+ 1 2 3))'
#:sci.impl{:loc {:line 1, :column 40, :end-line 1, :end-column 49}}