Split longer recordings

[crspeller]

Currently the audio summarization functionality will fail if the meeting is too long. (over 25MB) The first step to fixing this is being able to split up longer recordings and send them to the whisper API in chunks to avoid the API limitations: https://platform.openai.com/docs/guides/speech-to-text/introduction

Currently compression is used in this case: https://github.com/mattermost/mattermost-plugin-ai/blob/7a8c08f40e4051454ea68c872731e3b6e70c2123/server/meeting_summarization.go#L58

Go native implementation would be preferable to using ffmpeg.