.Net: Add support for audio transcription format

[SergeyMenshykh]

Context
Azure.AI.OpenAI SDK V2 added support for audio transcription format:

public enum AudioTranscriptionFormat
{
    Text,
    Simple,
    Verbose,
    Srt,
    Vtt,
}

that can be used by {Azure}OpenAIAudioToTextService classes:

var options = new AudioTranscriptionOptions()
{
    Granularities = ConvertToAudioTimestampGranularities(executionSettings!.Granularities),
    Language = executionSettings.Language,
    Prompt = executionSettings.Prompt,
    Temperature = executionSettings.Temperature,
    ResponseFormat = AudioTranscriptionFormat.Simple, // It's not supported by SK yet.
};

ToDo
Consider adding optional TranscriptionFormate property to the {Azure}OpenAIAudioToTextExecutionSettings class.

Notes
Decide whether the property should be released as part of the Azure.AI.OpenAI SDK V2 migration initiative or afterwards.

[SergeyMenshykh]

It appears that the property existed in the previous version of the Azure.AI.OpenAI SDK under the ResponseFormat name and already exists in the {Azure}OpenAIAudioToTextExecutionSettings classes.