Simplified Git fields on workers and worker versions

arkindex/process/api.py

arkindex/process/managers.py

...ker_repository_url_workerversion_revision_url_and_more.py

arkindex/process/models.py

arkindex/process/serializers/workers.py

arkindex/process/tests/test_corpus_worker_runs.py

arkindex/process/tests/test_docker_worker_version.py

arkindex/process/tests/test_user_workerruns.py

arkindex/process/tests/test_workerruns.py

arkindex/process/tests/test_workerruns_use_gpu.py

arkindex/process/tests/test_workers.py

arkindex/sql_validation/indexer_prefetch.sql