The U.S. economy headed into 2020 on a solid footing, with growth settling back to the roughly 2% pace that has prevailed during the decade-old economic expansion. Gross domestic product—the value of all goods and services produced across the economy—grew 2.3% last year, after rising at a seasonally and inflation-adjusted annual rate of 2.1% in the fourth quarter, the Commerce Department said Thursday. Year-over-year…