stream: use synchronous error validation on iteration helpers

 is no longer a generator function,
instead it returns a called generator so that validation can be
synchronous and not wait for the first iteration

Fixes: nodejs#41648

lib/internal/streams/operators.js

@@ -43,10 +43,9 @@ function map(fn, options) {
 
   validateInteger(concurrency, 'concurrency', 1);
 
-  const stream = this;
-
   return async function* map() {
     const ac = new AbortController();
+    const stream = this;
     const queue = [];
     const signal = ac.signal;
     const signalOpt = { signal };
@@ -157,7 +156,7 @@ function map(fn, options) {
         resume = null;
       }
     }
-  }();
+  }.call(this);
 }
 
 async function some(fn, options) {
@@ -238,7 +237,7 @@ function flatMap(fn, options) {
     for await (const val of values) {
       yield* val;
     }
-  }();
+  }.call(this);
 }
 
 function toIntegerOrInfinity(number) {