By Andrew Mills DOHA (Reuters) – Russia’s invasion of Ukraine has opened up diplomatic and commercial opportunities for gas exporter Qatar to expand energy sales to the West and bolster its alliance with Washington amid U.S. tensions with other Gulf Arab states. Qatar has sought a largely neutral stance on the conflict, but while trying to avoid choosing sides, it has signalled through its response that it can offer significant political and economic assistance to Western partners. With many European energy importers looking urgently for ways to ease their heavy dependence on Russia, Qatar has…