add Singularity support for "dockerFile" #1938

Job	Run time
No leftovers	4m 33s
CWL conformance (v1.0, docker)	3m 46s
CWL conformance (v1.0, singularity)	3m 23s
build_test_container	8m 56s
Test on macos-latest	6m 4s
CWL conformance (v1.0, podman)	3m 32s
CWL conformance (v1.1, docker)	4m 56s
cwltool release test	7m 40s
CWL conformance (v1.1, singularity)	6m 8s
CWL conformance (v1.1, podman)	5m 14s
Tox (3, 8, lint)	34s
Linters (lintreadme)	55s
Linters (shellcheck)	17s
Tox (3, 8, unit)	3m 48s
Linters (pydocstyle)	19s
Tox (3, 8, bandit)	30s
Tox (3, 8, mypy)	4m 2s
CWL conformance (v1.2, docker)	7m 1s
Tox (3, 9, lint)	31s
Tox (3, 9, unit)	3m 4s
CWL conformance (v1.2, singularity)	7m 11s
Tox (3, 9, bandit)	26s
Tox (3, 9, mypy)	2m 54s
Tox (3, 10, lint)	29s
CWL conformance (v1.2, podman)	7m 8s
Tox (3, 10, unit)	6m 38s
Tox (3, 10, bandit)	28s
CWL conformance (v1.2, docker, --fast-parser)	7m 7s
Tox (3, 10, mypy)	7m 37s
Tox (3, 11, lint)	32s
Tox (3, 11, unit)	6m 9s
Tox (3, 11, bandit)	31s
Tox (3, 11, mypy)	7m 20s
Tox (3, 12, lint)	33s
Tox (3, 12, unit)	3m 52s
Tox (3, 12, bandit)	35s
Tox (3, 12, mypy)	6m 4s
	2h 20m 47s

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