py(deps): Add pytest-xdist

See also:
- https://pypi.org/project/pytest-xdist/
- https://github.com/pytest-dev/pytest-xdist

Author: tony

Diff for: poetry.lock

@@ -76,6 +76,7 @@ pytest-rerunfailures = "*"
 pytest-mock = "*"
 pytest-cov = "*"
 pytest-watcher = "*"
+pytest-xdist = "*"
 gp-libs = "~0.0.4"
 
 [tool.poetry.group.coverage.dependencies]