Add device flag to TTS CLI

[jaketae]

Context

In #2855, we added a new .to(device) API for the TTS class, allowing users to freely choose the accelerator backend of their choice. For further ease of access, we want to incorporate this new feature into the TTS CLI, which currently only allows users to specify the device via --use_cuda.

Solution

Add a new --device flag to the TTS CLI. Now, uses can do

$ tts --text "hello world" --device cuda:1  # specify cuda device
$ tts --text "hello world" --device mps  # use apple silicon

[jaketae]

Hi @erogol, this is a quick follow-up to the previous PR. In this PR, we add a --device flag to the TTS CLI. Let me know what you think! Thank you.