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

PR Close #26060

packages/router/src/operators/switch_tap.ts

@@ -1,29 +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, ObservableInput, from} from 'rxjs';
-import {map, switchMap} from 'rxjs/operators';
-
-/**
- * Perform a side effect through a switchMap for every emission on the source Observable,
- * but return an Observable that is identical to the source. It's essentially the same as
- * the `tap` operator, but if the side effectful `next` function returns an ObservableInput,
- * it will wait before continuing with the original value.
- */
-export function switchTap<T>(next: (x: T) => void|ObservableInput<any>):
-    MonoTypeOperatorFunction<T> {
-  return function(source) {
-    return source.pipe(switchMap(v => {
-      const nextResult = next(v);
-      if (nextResult) {
-        return from(nextResult).pipe(map(() => v));
-      }
-      return from([v]);
-    }));
-  };
-}