The `onlyCritical` parameter of RobotPublisher does not work correctly because criticality has been obsolete since RobotFramework 4.0.

If you set `onlyCritical: true`, all the tests are considered non-critical thus the step will always be success status.

Since RobotFramework 4.0, the criticality of tests is removed and does not output the "critical" attribute in output.xml.

As a result, the critical attribute can no longer be retrieved when parsing ouput.xml, and all tests are determined to be non-critical.

(https://github.com/robotframework/robotframework/issues/3624)

Other changes include removing the critical attribute from test elements in output.xml and changes to the result related APIs.