Get rid of CustomTask c'tor taking 3 handlers.
If the done handler needs to be called only on
success or an error, add explicit 3rd arg of CallDoneIf type.
Task-number: QTCREATORBUG-29834
Change-Id: I10e55415587e6cac46620dd5177ad8269584583c
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Not all classes derived from TaskItem are tasks,
but the common denominator is that all may be placed
inside a group: thus GroupItem sounds more appropriate.
Addresses the 10th point in the bugreport below.
Task-number: QTCREATORBUG-28741
Change-Id: I94d728a8e39ec732810f2e5bbe6b9a76f3bc387c
Reviewed-by: Qt CI Patch Build Bot <ci_patchbuild_bot@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: hjk <hjk@qt.io>
