Faster keywordize

[bsless]

Implement walk with protocols and keywordize keys with it.
Gives about 2x speedup

left to do: decide on an implementation for cljs

[bsless]

@ikitommi do you want to extend this solution to cljs or keep it just for clj?

[bsless]

Decided to split the implementation off only for Clojure since cljs is built differently, don't even know how walk is implemented for it

[bsless]

@ikitommi are there any blocking items for a review? I'd be happy to clear them if so.

[bsless]

New and improved version, about 4x faster for input

{"int" "10", "ints" ["1" "2" "3"], "map" {:1 "1", "2" "2"}}

[bsless]

Open question - how can we be sure this does not introduce regressions for users who upgrade?

[bsless]

Added generative test to validate my assumption

[ikitommi]

Thanks!