By Guy Faulconbridge ST PETERSBURG, Russia, June 2 (Reuters) - A right-wing U.S. influencer, a serving U.S. official and a German retail billionaire are due to attend President Vladimir Putin's "Russian Davos" on Wednesday as the Kremlin grapples with stalled growth and a confrontation with the West over the Ukraine war. Russia's premier investment forum, the fifth since Russia sent troops into Ukraine in 2022, opens just hours after a deadly drone and missile attack on Kyiv which Russia said was in response to a deadly attack on a dormitory in Russian-controlled Luhansk.