Add ISpeechToTextClient implementation support

[rogerbarreto]

This implementation adds support to the latest ISpeechToTextClient abstraction from the Microsoft.Extensions.AI.Abstractions package.

• Updated Runtime version
• Added implementation for the client using same pattern With for adding options.
• Added Demo for the new client
• Minor warning fixes (blank lines, missing headers, unused usings)

[sandrohanea]

Thanks a lot @rogerbarreto for this contribution!

It was on my list to work on this support (when I saw that MEAI PR was merged).

Added small comments, let me know what do you think.