Refactor MusicHistoryRequest and MusicRecommendationRequest to have albums, stations and playlists as properties

[rudrankriyam]

With the current implementation, it feels confusing to use and get an array of albums from the items:

var recentlyPlayedAlbums: [Album] = []

let request = MusicHistoryRequest(for: .recentlyPlayed)
let response = try await request.response()

recentlyPlayedAlbums = response.items.compactMap { item in 
    switch item {
        case .album(let album): return album
        default: return nil
    }
}

It would be nice if you could directly fetch the items:

var recentlyPlayedAlbums: Albums?

let request = MusicHistoryRequest(for: .recentlyPlayed)
let response = try await request.response()

recentlyPlayedAlbums = response.albums