In AngularFireFunctions allow for calling `httpsCallableFromURL`

Feature request
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In AngularFireFunctions allow for calling `httpsCallableFromURL` (https://firebase.google.com/docs/reference/js/functions.md#httpscallablefromurl), similar to current call call to `httpsCallable`. With Firebase Cloud Functions V2 this is the only way for calling that new functions (since, they are still in preview mode: https://firebase.google.com/docs/functions/beta/callable#call_the_function).

從 AngularFireFunctions 入口點開始，將其現有的 httpsCallable 支援與 issue 中描述的 Firebase httpsCallableFromURL API 進行比較。當 AngularFireFunctions 能夠透過 URL 呼叫 Cloud Functions V2 端點，且行為與現有的 callable 支援一致時，即視為完成；如果實作過程識別出相關測試，請新增或更新這些測試。

由索引模型根據 Issue 內容生成。