js: fix rand build, properly use key values on map, add rand.string (#12020)

vlib/rand/rand.v

@@ -38,19 +38,6 @@ __global (
 	default_rng &PRNG
 )
 
-// init initializes the default RNG.
-fn init() {
-	default_rng = new_default()
-	C.atexit(deinit)
-}
-
-fn deinit() {
-	unsafe {
-		default_rng.free() // free the implementation
-		free(default_rng) // free the interface wrapper itself
-	}
-}
-
 // new_default returns a new instance of the default RNG. If the seed is not provided, the current time will be used to seed the instance.
 [manualfree]
 pub fn new_default(config config.PRNGConfigStruct) &PRNG {