Sending a password reset mail

### [REQUIRED] Step 2: Describe your environment

* Operating System version: not relevant
* Firebase SDK version: 2.4.0
* Firebase Product: auth
* .NET version: not relevant
* OS: not relevant

### [REQUIRED] Step 3: Describe the problem

The SDK is missing a method SendPasswordResetLinkAsync

More precisely, the use case would be to allow ReturnOobLink to be set to false EVEN IF we are authenticated

https://github.com/firebase/firebase-admin-dotnet/blob/master/FirebaseAdmin/FirebaseAdmin/Auth/Users/EmailActionLinkRequest.cs#L62

At the moment, we need to manually instanciate a HttpClient and to send the HTTP request like described at https://firebase.google.com/docs/reference/rest/auth?hl=fr#section-send-password-reset-email

Our exact use case is to create the user with a random password and then to send him a reset password link (but directly from the firebase servers, not from our servers)

If there is a better way (without using my own SMTP server), please share it with me

#### Steps to reproduce:

not relevant

#### Relevant Code:

```
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Start with FirebaseAdmin/FirebaseAdmin/Auth/Users/EmailActionLinkRequest.cs at the referenced ReturnOobLink setting, then compare its behavior with the Firebase Auth REST send-password-reset-email documentation. The work is complete when the SDK supports sending a Firebase-hosted password reset link for an authenticated workflow without requiring the caller to create its own HttpClient or SMTP server.

Written by the indexing model from the issue text.