Add notebooks for recent features: Live, Ephemeral tokens, Multispeaker

[MarkDaoust]

Description of the feature request:

Here is seed material. It would be great if the Devrel team could pick these up and organize/finalize/merge them:

A bunch of live features were added recently, here are examples:

https://drive.google.com/file/d/1vEMe7UcErgu-FaqSiMum9UN-n8aqhIXR/view?usp=drive_link

Multispeaker audio (maght need a warning about cost + quota):

https://drive.google.com/file/d/1-X9WLFk6onpIujlAMFik9nV890oakskk/view?usp=drive_link

Ephemeral tokens:

https://drive.google.com/file/d/1npb20gzGgSm6HWmFd4Hu2lFoKy5NOs0M/view?usp=drive_link

[Giom-V]

Multispeakers already has an example in the TTS notebook: https://github.com/google-gemini/cookbook/blob/main/quickstarts/Get_started_TTS.ipynb