Errors is text editor are sticky with new ouput pane until new outputpane is cleared

Errors is text editor are sticky with new ouput pane until new outputpane is cleared.

In QDS 4.5 without the output pane issues are cleared when a file is saved.

with QDS 4.6 the new ouput pane keeps issues from beeing removed from the text editor until the new ouput pane is explicitly cleared.

How to reproduce:

1) Create a syntax error in QML
2) Run app
3) Issue is created in all output panes/an error text marker is created
4) Fix the issue
5) save the file
6) The issue related to the syntax error is removed from old output pane

Error:

The syntax issue is not removed from new ouput pane and the text marker does persist.

MessageModel keeps a list of all ProjectExplorer::Task tasks.

Each task keeps a smart pointer on a text marker:
std::shared_ptr<TextEditor::TextMark> m_mark;

This is why the text marker does perisist.

ProjectExplorer::TaskHub::tasksCleared is emitted in this case which clears a complete category.