Merge branch 'master' into firedrakeConnection-functional to get rid of py2.6 CL

.editorconfig

.github/workflows/ci.yml

.gitlab-ci.yml

doc/misc.rst

meshmode/discretization/connection/opposite_face.py

meshmode/mesh/__init__.py

meshmode/mesh/generation.py

meshmode/mesh/processing.py

meshmode/mesh/refinement/no_adjacency.py

meshmode/version.py

setup.py

test/test_meshmode.py

test/test_refinement.py