Speed up CWL conformance tests to ~10 minutes total using the pytest plugin

[unito-bot]

cwltool runss its CWL conformance tests in about 10 minutes using a pytest plugin to do everything in one process and make the conformance tests PyTest tests. See:

https://github.com/common-workflow-language/cwltool/blob/6c86caa0571fd186d90a6600e0bb405596d4a5e0/conformance-test.sh#L90

https://github.com/common-workflow-language/cwltool/blob/6c86caa0571fd186d90a6600e0bb405596d4a5e0/conformance-test.sh#L152

https://matrix.to/#/!rnpqRUgCiUQaGeqAWG:matrix.org/$FZklLQT7I0KSAUxlqHfKPGM7iSDNKRWcKiMKhnh0r-M?via=matrix.org&via=gitter.im

┆Issue is synchronized with this Jira Story
┆Issue Number: TOIL-1689