clean: Remove unused functionalities

docs/coverage.svg

docs/docstr_coverage_badge.svg

docs/source/index.rst

run_tests.sh

src/dsgs/operators/data.py

src/dsgs/utils/checkpoint.py

src/dsgs/utils/communications.py

src/dsgs/utils/communicators.py

tests/mpi/test_mpi_inpainting_operator.py

tests/operators/test_inpainting_model.py

tests/utils/test_communications.py

tests/utils/test_communicators.py