SK Hynix memory chain flowing into Korea ETF beta Hyperscaler AI capex data-center buildout toward HBM HBM4 stack advanced packaging= bottleneck if tight Constrained supply HBM + DRAM pricing firm SK Hynix earnings lifts Seoul-share price the shared driver of ETF beta Seoul-share returns heavy weight light weight EWY heavier SK Hynix weight more return per point FLKR lighter SK Hynix weight less return per point