Improve map gen creation performance

[bsless]

This MR improves the performance for creating a map gen ~x5, mostly by removing a call to satisfies?, and further by choosing performant functions in the implementation.

[ikitommi]

Thanks for the improvements! This only mainly effects (e.g. satifies?) the case where the generator is not cached, right?

;; no cache
(mg/generate [:map [:x :int] [:y :int]])

;; instance cache
(let [s (m/schema [:map [:x :int] [:y :int]])]
  (mg/generate s))
  
;; cached function
(let [g (mg/generator [:map [:x :int] [:y :int]])]
  (mg/generate g))

[ikitommi]

On my machine, merging this. Thanks!!

(p/bench (mg/generate [:map [:x :int] [:y :int]]))
;; 18,5µs => 5,6 µs (-70%)

(let [s (m/schema [:map [:x :int] [:y :int]])]
  (p/bench (mg/generate s)))
;; => 3.3µs => 2.8µs (-15%)

(let [g (mg/generator [:map [:x :int] [:y :int]])]
  (p/bench (mg/generate g)))
;; => 2.8µs => 2.6µs (-8%)

[bsless]

Gladly :)
For reference, this is the use case that made me care about construction performance
https://github.com/bsless/fsm-test-check/blob/master/examples/add_delete_tx_malli.clj