Hide audio tab when the user has no audio

[planarvoid]

Fixes #11361

This PR hides the audio tab in the Media activity when the user has no audio. The activity now listens to the event and refreshes the tab layout style if there is a change to the number of audio files.

To test:

• Go to a site without Audio media
• Go to the My Site/Media
• Check that the "Audio" tab is not visible
• Go to Calypso and add an audio file to the site media library
• Pull to refresh in the app
• The "Audio" appears
• Click on the "Audio" tab
• The audio file is visible on the screen
• Remote the audio file in Calypso
• Pull to refresh in the app
• The "Audio" tab disappears and the "All" tab is automatically selected

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can test the changes on this Pull Request by downloading the APK here.

[ashiagr]

Works as described 👍.

Just that "Upload Media" is visible again in the Audio tab if we delete audio file from the app and return to the media screen. Not sure if we want to select "All" tab in this scenario.

[planarvoid]

thanks for the check @ashiagr !

I've implemented the fix in 882f665

[ashiagr]

LGTM, 🚢.