build: roll up to named .js files rather than 'index.js' (#19190)

PR Close #19190

packages/router/upgrade/package.json

@@ -1,7 +1,7 @@
 {
   "name": "@angular/router/upgrade",
-  "typings": "./index.d.ts",
+  "typings": "./upgrade.d.ts",
   "main": "../bundles/router-upgrade.umd.js",
-  "module": "../esm5/upgrade/index.js",
-  "es2015": "../esm15/upgrade/index.js"
+  "module": "../esm5/upgrade.js",
+  "es2015": "../esm2015/upgrade.js"
 }

packages/router/upgrade/rollup.config.js

@@ -17,7 +17,7 @@ const globals = {
 };
 
 export default {
-  entry: '../../../dist/packages-dist/router/esm5/upgrade/index.js',
+  entry: '../../../dist/packages-dist/router/esm5/upgrade.js',
   dest: '../../../dist/packages-dist/router/bundles/router-upgrade.umd.js',
   format: 'umd',
   exports: 'named',

packages/router/upgrade/tsconfig-build.json

@@ -19,7 +19,7 @@
   "angularCompilerOptions": {
     "annotateForClosureCompiler": true,
     "strictMetadataEmit": true,
-    "flatModuleOutFile": "index.js",
+    "flatModuleOutFile": "upgrade.js",
     "flatModuleId": "@angular/router/upgrade"
   }
 }