WASHINGTON — Russia freed WNBA star Brittney Griner on Thursday in a high-profile prisoner exchange, as the U.S. released notorious Russian arms dealer Viktor Bout but failed to win freedom for another American, Paul Whelan, who has been jailed for nearly four years.The deal, the second in eight months amid tensions over Russia’s invasion of Ukraine, secured the release of the most prominent American detained abroad and achieved a top policy goal for President Joe Biden. But it carried what U.S. officials …