Support new monthly audience metric

[sigma67]

Is your feature request related to a problem? Please describe.

Popular channels replace subscribers with monthly audience metric

https://music.youtube.com/channel/UCqJnSdHjKtfsrHi9aI-9d3g

Describe the solution you'd like

Parse monthly audience metric correctly into separate attribute monthlyListens and set subscribers to None as it is replaced in that case

Describe alternatives you've considered

Additional context

• https://support.google.com/youtubemusic/answer/15621827?visit_id=638820282146302918-1351610219&p=ytmMonthlyListens&rd=1
• https://9to5google.com/2025/01/07/youtube-music-monthly-audience-metric/

To display Monthly Audience your channel must meet requirements:

    Your channel is an [Official Artist Channel](https://support.google.com/youtube/answer/7336634) (OAC).
    Your channel has more than 100,000 subscribers.
    Your channel’s Monthly Audience is over 50,000 listeners.

If your channel does not meet these requirements, it will continue to only display the Subscriber count.