Allow for apiserver not returning outputFolder
dxpy: add no_parent_job, no_parent_analysis to find_executions

- Also, fix test that was half-fixed in 6cc223bafe80057806901d90540b496362912d88
PTFM-10147: dxpy: Support setting stage-specific systemRequirements in workflows
PTFM-10147: dx: add/update stage --instance-type support

- Also add --instance-type-help for printing list of instance types