Two Part (Double-blind Inclisiran Versus Placebo [Year 1] Followed by Open-label Inclisiran [Year 2]) Randomized Multicenter Study to Evaluate Safety, Tolerability and Efficacy of Inclisiran in Children (6 to Less Than 12 Years) With Heterozygous Familial Hypercholesterolemia and Elevated LDL- Cholesterol | Arctuva