feat: add option to disable route extraction feature

### Command

build

### Description

When migrating apps to SSR, route extraction basically gets in the way and makes it harder to understand where the issue/error is coming from, as it tries to run before everything else either during build or server.

Instead of fixing other SSR related errors, I have to go and fix route extraction issues.

Also, there is no way to know if route extraction is happening. But even if it was possible the code would be full of checks on what mode is Angular running, and having to deal with all the states instead of just handling a normal case of -> open the url -> render angular -> serve html.

### Describe the solution you'd like

Add a flag to disable route extraction during build or serve totally, at least just for development purposes.
When routes are dynamically loaded based on config, having the extraction happen before the config can be loaded breaks the dynamic apps. If I build my app with a config that has 3 routes, and then on runtime I want to use another config.json file to load other routes (that also include the first three but with different configs), would cause my app to misbehave because of the initial extracted routes.

---

`NG_BUILD_PARTIAL_SSR=1` partially solves this by skipping the route extraction and doing it initial request.

### Repo
Comment out line 9 to better understand that serving or building the app is painful, even though on normal conditions opening localhost:4200/config.json loads fine.

https://github.com/eneajaho/dx-issue/blob/main/src/main.server.ts#L9

まず build コマンドと既存の NG_BUILD_PARTIAL_SSR=1 の動作を確認し、次にリンク先のサンプルリポジトリで src/main.server.ts の 9 行目を使って問題を再現します。build または serve 中のルート抽出を flag で無効にでき、動的に読み込まれるルートを持つアプリケーションが引き続き動作すれば完了です。

索引モデルが issue の本文から書いたものです。