ci: azure: use xdist with pluggymaster
ci: azure: use xdist with pluggymaster

nicoddemus/pytest,RonnyPfannschmidt/pytest,pytest-dev/pytest,The-Compiler/pytest,Akasurde/pytest,The-Compiler/pytest,alfredodeza/pytest,tomviner/pytest,tomviner/pytest,nicoddemus/pytest,markshao/pytest