In previous version of tsickle abstract class methods were materialized.
The change resulted in 6Kb savings in angular.io bundle.
This change also required the removal of `@private` and `@return` type
annotation as it is explicitly dissalowed by tsickle.
NOTE: removed casts in front of `makeDecorator` due to:
https://github.com/angular/devkit/issues/45
```
14938 Jul 19 13:16 0.b19e913fbdd6507d346b.chunk.js
1535 Jul 19 13:16 inline.d8e019ea3cfdd86c2bd0.bundle.js
589178 Jul 19 13:16 main.54c97bcb6f254776b678.bundle.js
34333 Jul 19 13:16 polyfills.4a3c9ca9481d53803157.bundle.js
14938 Jul 18 16:55 0.b19e913fbdd6507d346b.chunk.js
1535 Jul 18 16:55 inline.0c83abb44fad9a2768a7.bundle.js
582786 Jul 18 16:55 main.ea290db71b051813e156.bundle.js
34333 Jul 18 16:55 polyfills.4a3c9ca9481d53803157.bundle.js
main savings: 589178 - 582786 = 6,392
```
PR Close#18236
This fixes a flicker when transitioning from server rendered page to client rendered page in lazy loaded routes by waiting for the lazy loaded route to finish loading, assuming initialNavigation on the route is set to 'enabled'.
Fixes#15716
