Case C-148/19 P: Judgment of the Court (Seventh Chamber) of 7 May 2020 — BTB Holding Investments SA, Duferco Participations Holding SA v European Commission, Foreign Strategic Investments Holding (FSIH) (Appeal — State aid — Regional aid to the steel industry — Decision declaring that aid incompatible with the common market — Concept of ‘State aid’ — Advantage — Private operator test — Manifest error — Burden of proof — Limits of judicial review)