httpTimeout option in initializeApp

**Is your feature request related to a problem? Please describe.**
In the Python implementation of firebase_admin, there is an option on [initialize_app](https://firebase.google.com/docs/reference/admin/python/firebase_admin#initialize_app) that allows the httpTimeout to be set manually. There is no such implementation in NodeJS.

**Describe the solution you'd like**
The desired solution is to have the same functionality of httpTimeout in the Python firebase_admin, implemented for the NodeJS firebase-admin.

**Additional context**
Using firebase-admin version 9.4.2

从 Node.js firebase-admin 的 initializeApp 入口点开始，将其选项与链接的 Python initialize_app 参考进行比较。完成的标准是 Node.js 调用方可以通过 initializeApp 设置 httpTimeout，并且配置的超时得到遵守；使用相关的 initializeApp 测试验证该行为。

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