Several adjustments to UI as discussed with Håkon and Alireza.
* add link/unlink command to right-click menu of axis
* select curve in project tree when clicking on legend item
* make sure internal legend is always visible when toggling plot
* fix issue when using sub plot as data source for axis range
Always create plots using Qwt
Always create plot for command "New Summary Plot"
#9103 : Fix missing updates in multiselect field update operation
Add Open Summary Plot Editor
Trigger missing load of data
Enable data source display for first realization of an ensemble
Always show legend text
Set version to 2022.06.0-RC-02
* Guard use of back() on empty vector
* Add "Show Data Sources" to ensemble realizations
* Update summary plot as summary curve collection is not visible in tree view
* Set selection manager root in RiaApplication
* Always close both main windows if present
* Add copy/paste of summary multi plot
* Add test for RiuMainWindow::instance() before use
* Remove duplicated code
* Multiple Tree Views : Use getTreeViewWithItem() to find correct tree view
* Minor UI adjustments
* Make sure the subplot selected in the tree is shown in the multiplot viewer.
* Clean up multiplot toolbar handling a bit
* Remove old summary plot toolbar.
