Add compiler meta hint info

[dkarvik]

It's come up many times on slack that this is generally used wrong and is to be discouraged,

[puredanger]

Broadening this to include compiler meta hints like ^:const, ^:static, ^:once, etc and var meta like ^:tag, ^:arglists, etc. Might make sense in the FAQ, or perhaps on https://clojure.org/reference/compilation or https://clojure.org/reference/vars.