WEB-1577 Dart, DartUnit run configuration: on adding a new configuration existing configurations are overwritten with new configuration settings
(cherry picked from commit 81c9a13)

CR-WS-123
WEB-1577 Dart, DartUnit run configuration: on adding a new configuration existing configurations are overwritten with new configuration settings

after review
(cherry picked from commit dd1d476)

CR-WS-123