Extract RootTag case of translateTypeAnnotation from the flow and typescript folders in parsers-primitives (#34901)

Summary:
This PR aims to reduce code duplication by extracting `emitRootTag` logic from the flow and typescript folders into a shared parsers-primitives file. It is a task of https://github.com/facebook/react-native/issues/34872:
> Extract the content of the case 'RootTag' (Flow TypeScript) into a single emitRootTag function in the parsers-primitives.js file. Use the new function in the parsers.

~~Note that https://github.com/facebook/react-native/issues/34898 should be merged first. I rebased on it's branch.~~

## Changelog

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[Internal] [Changed] - Extract RootTag case of translateTypeAnnotation from the flow and typescript folders in parsers-primitives

Pull Request resolved: https://github.com/facebook/react-native/pull/34901

Test Plan:
All tests are passing, with `yarn jest react-native-codegen`:
<img width="934" alt="image" src="https://user-images.githubusercontent.com/40902940/194777150-6136c1b6-11f8-4e21-829b-fda418b6925c.png">

Reviewed By: cipolleschi

Differential Revision: D40212553

Pulled By: cipolleschi

fbshipit-source-id: eadbbfb5cf6dfa6c966f4c08a5d9372a3470b621

packages/react-native-codegen/src/parsers/__tests__/parsers-primitives-test.js

@@ -15,7 +15,8 @@ const {
   emitBoolean,
   emitNumber,
   emitInt32,
-} = require('../parsers-primitives.js');
+  emitRootTag,
+} = require('../parsers-primitives');
 
 describe('emitBoolean', () => {
   describe('when nullable is true', () => {
@@ -94,3 +95,29 @@ describe('emitNumber', () => {
     });
   });
 });
+
+describe('emitRootTag', () => {
+  const reservedTypeAnnotation = {
+    type: 'ReservedTypeAnnotation',
+    name: 'RootTag',
+  };
+
+  describe('when nullable is true', () => {
+    it('returns nullable type annotation', () => {
+      const result = emitRootTag(true);
+
+      expect(result).toEqual({
+        type: 'NullableTypeAnnotation',
+        typeAnnotation: reservedTypeAnnotation,
+      });
+    });
+  });
+
+  describe('when nullable is false', () => {
+    it('returns non nullable type annotation', () => {
+      const result = emitRootTag(false);
+
+      expect(result).toEqual(reservedTypeAnnotation);
+    });
+  });
+});

packages/react-native-codegen/src/parsers/flow/modules/index.js

@@ -37,6 +37,7 @@ const {
   emitBoolean,
   emitNumber,
   emitInt32,
+  emitRootTag,
 } = require('../../parsers-primitives');
 const {
   IncorrectlyParameterizedGenericParserError,
@@ -87,10 +88,7 @@ function translateTypeAnnotation(
     case 'GenericTypeAnnotation': {
       switch (typeAnnotation.id.name) {
         case 'RootTag': {
-          return wrapNullable(nullable, {
-            type: 'ReservedTypeAnnotation',
-            name: 'RootTag',
-          });
+          return emitRootTag(nullable);
         }
         case 'Promise': {
           assertGenericTypeAnnotationHasExactlyOneTypeParameter(

packages/react-native-codegen/src/parsers/parsers-primitives.js

@@ -15,6 +15,7 @@ import type {
   Int32TypeAnnotation,
   NativeModuleNumberTypeAnnotation,
   Nullable,
+  ReservedTypeAnnotation,
 } from '../CodegenSchema';
 
 const {wrapNullable} = require('./parsers-commons');
@@ -39,8 +40,16 @@ function emitNumber(
   });
 }
 
+function emitRootTag(nullable: boolean): Nullable<ReservedTypeAnnotation> {
+  return wrapNullable(nullable, {
+    type: 'ReservedTypeAnnotation',
+    name: 'RootTag',
+  });
+}
+
 module.exports = {
   emitBoolean,
   emitInt32,
   emitNumber,
+  emitRootTag,
 };

packages/react-native-codegen/src/parsers/typescript/modules/index.js

@@ -37,6 +37,7 @@ const {
   emitBoolean,
   emitNumber,
   emitInt32,
+  emitRootTag,
 } = require('../../parsers-primitives');
 const {
   IncorrectlyParameterizedGenericParserError,
@@ -199,10 +200,7 @@ function translateTypeAnnotation(
     case 'TSTypeReference': {
       switch (typeAnnotation.typeName.name) {
         case 'RootTag': {
-          return wrapNullable(nullable, {
-            type: 'ReservedTypeAnnotation',
-            name: 'RootTag',
-          });
+          return emitRootTag(nullable);
         }
         case 'Promise': {
           assertGenericTypeAnnotationHasExactlyOneTypeParameter(