By Hannah Lang WASHINGTON (Reuters) – The dollar was on track to post its best year since 2015 on Friday in the last trading day of a year dominated by Federal Reserve rate hikes and fears of a sharp slowdown in global growth. As 2022 draws to a close, the dollar was set to notch a 7.9% annual gain against a basket of currencies – its biggest annual jump in seven years. But the dollar has pared gains in recent weeks as investors look for signs of when the Fed’s interest-rate-hiking cycle might end. The Fed has raised rates by a total of 425 basis points since March in an attempt to curb surgin…