Declare dependencies between helpers in the declaritive fashion introduced by microsoft#35967

Author: weswigham

src/compiler/factory.ts

@@ -278,6 +278,7 @@ namespace ts {
         name: "typescript:spread",
         importName: "__spread",
         scoped: false,
+        dependencies: [readHelper],
         text: `
             var __spread = (this && this.__spread) || function () {
                 for (var ar = [], i = 0; i < arguments.length; i++) ar = ar.concat(__read(arguments[i]));
@@ -286,7 +287,6 @@ namespace ts {
     };
 
     export function createSpreadHelper(context: TransformationContext, argumentList: readonly Expression[], location?: TextRange) {
-        context.requestEmitHelper(readHelper);
         context.requestEmitHelper(spreadHelper);
         return setTextRange(
             createCall(

src/compiler/transformers/es2018.ts

@@ -1096,6 +1096,7 @@ namespace ts {
         name: "typescript:asyncGenerator",
         importName: "__asyncGenerator",
         scoped: false,
+        dependencies: [awaitHelper],
         text: `
             var __asyncGenerator = (this && this.__asyncGenerator) || function (thisArg, _arguments, generator) {
                 if (!Symbol.asyncIterator) throw new TypeError("Symbol.asyncIterator is not defined.");
@@ -1111,7 +1112,6 @@ namespace ts {
     };
 
     function createAsyncGeneratorHelper(context: TransformationContext, generatorFunc: FunctionExpression, hasLexicalThis: boolean) {
-        context.requestEmitHelper(awaitHelper);
         context.requestEmitHelper(asyncGeneratorHelper);
 
         // Mark this node as originally an async function
@@ -1132,6 +1132,7 @@ namespace ts {
         name: "typescript:asyncDelegator",
         importName: "__asyncDelegator",
         scoped: false,
+        dependencies: [awaitHelper],
         text: `
             var __asyncDelegator = (this && this.__asyncDelegator) || function (o) {
                 var i, p;
@@ -1141,7 +1142,6 @@ namespace ts {
     };
 
     function createAsyncDelegatorHelper(context: TransformationContext, expression: Expression, location?: TextRange) {
-        context.requestEmitHelper(awaitHelper);
         context.requestEmitHelper(asyncDelegator);
         return setTextRange(
             createCall(