(Fixes typos in third and seventh paragraphs) WASHINGTON (Reuters) -Voters in Georgia and Alabama will pick candidates for the U.S. Congress and other offices in Tuesday primaries testing former President Donald Trump’s power over his Republican Party ahead of the Nov. 8 midterm elections. Arkansas will also hold nomination contests while Texas will hold run-off elections for races that were unresolved in that state’s March 1 primaries. Here are seven races to watch: HERSCHEL WALKER’S U.S. SENATE BID In Georgia, Trump-backed Herschel Walker, a former professional football player with scant pol…