Add support for images with various qualities

[defagos]

As a developer integrating Pillarbox I might need higher or lower resolutions for artworks retrieved by Pillarbox. Currently a single resolution is supported but on small / large layouts this might be superfluous or insufficient.

Hints

• We could simply turn current image sources into arrays of sources with various qualities (optional), then have lazy retrieval be made for some desired quality.
• Internal usage (e.g. Control Center) would request one of the qualities.
• Qualities should likely be loosely defined (maybe low, medium and high) with recommended resolutions.

Acceptance criteria

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Tasks

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