Add `for` and `id` attributes to the customizer hue picker, so labels are explicitly associated. Move picker outside of `label` element. Add `label` value for Twenty Seventeen, Twenty Nineteen, and Twenty Twenty.
Props afercia, subrataemfluence, dlh, jorbin, sainathpoojary, abcd95, mleraygp, joedolson.
Fixes#42078.
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