Look into changing the focal-point picker inside the customizer background control

[abaicus]

Based on this comment.

Description:

I tried reworking how the control functions, but that has proven tedious as it generates infinite update loops because of type coercion inside the core focal point picker [...] Maybe we can look into reworking the focal point picker control. We can replace it with a third-party one, or perhaps use another control (I would suggest using the point matrix control, as I don't see a massive benefit in having the amount of control we offer now for the positioning).