Revert "refactor(router): cleanup to navigation stream for readability" and associated changes (#26060)

PR Close #26060

packages/router/src/operators/check_guards.ts

@@ -1,24 +0,0 @@
-/**
- * @license
- * Copyright Google Inc. All Rights Reserved.
- *
- * Use of this source code is governed by an MIT-style license that can be
- * found in the LICENSE file at https://angular.io/license
- */
-
-import {MonoTypeOperatorFunction, Observable, from, of } from 'rxjs';
-import {map, mergeMap} from 'rxjs/operators';
-
-import {NavigationTransition} from '../router';
-
-export function checkGuards(): MonoTypeOperatorFunction<NavigationTransition> {
-  return function(source: Observable<NavigationTransition>) {
-
-    return source.pipe(mergeMap(t => {
-      if (!t.preActivation) {
-        throw new Error('PreActivation required to check guards');
-      }
-      return t.preActivation.checkGuards().pipe(map(guardsResult => ({...t, guardsResult})));
-    }));
-  };
-}