Fix misc playlist issues

[raymondjacobson]

Add playlist update locking mechanism to prevent optimistic re-fetching from clobbering pending updates.

Tested:

• Repeated adding and removing tracks in 1 tab
• Repeated adding and removing tracks in 2 tabs concurrently. If doing two tabs, it's still possible to get into weird states, but it's a much rarer edge case where you're adding multiple tracks in multiple tabs before any of them confirm.

A simpler solve would be to just not refetch before update while something is in the confirmer, but that isn't super great because we handle updates async and still could bite you if you're on the add tracks to playlist menu and just clicking add repeatedly.

Fixes two additional bugs:

• We don't render the playlist name until the artwork loads. This was from an old way of doing this and was causing issues loading playlists entirely
• Playlist library was not getting created from a fresh account that had no library and was making playlists. Add a couple saga helpers to fix, for now since all that logic still lives in saga land.

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[rickyrombo]

so iiuc we grab a mutex, do our operation, and the next operation will wait for that mutex before doing its operation, at which point even if it refetches it'll be up to date?

[raymondjacobson]

so iiuc we grab a mutex, do our operation, and the next operation will wait for that mutex before doing its operation, at which point even if it refetches it'll be up to date?

yeah, but the mutex lets go right when we insert the change into the confirmer. i don't know if i like it though, doing another pass at the simpler solve of just not fetching when we have optimistic state.