Selection Editor

Selection Editor is a new panel that allows saving and combining many selections of different types using a boolean expression.

Selection Editor has:

1. Data producer field that is set based on the source of the active selection.
   1. If the source of the active selection changes, the Data producer will change as well, and any saved selection will be deleted.
2. Element type field that is set based on the element type of the active selection.
   1. If a selection is saved and a new active selection is made that has a different element type, the user will be prompted to decide if he wants to change the element type to add the new active selection. Doing so will result in deleting the saved selection.
3. Expression string that is set by the user, and it is also automatically filled while adding new selections.
4. Saved Selections table that lists the name, which is used to define the expression, and the type of the selection.
   1. If the user selects a selection from the Saved Selections table, and the active view is a render-view, the selected selection will be interactively shown. Deselecting the selected selection hides the selected selection from the render-view.
5. Add Active Selection button that adds the active selection to the list of saved selections.
6. Remove Selected Selection button that removes the selected saved selection from the list of saved selections.
7. Remove All Selections button that removes all saved selections from the list of saved selections.
8. Activate Combined Selections button that sets the combined saved selections as the active selection.

An example of a combined selection created using the selection editor is shown below.

To accommodate the creation of the Selection Editor panel, the following changes were also completed:

1. SelectionQuerySource now is implemented using vtkSelectionSource. vtkQuerySelectionSource has been removed since it's no longer needed.
2. AppendSelections filter proxy has been created using vtkAppendSelection to combine many selections of different types using a boolean expression.
3. Every view (render/context/spreadsheet) and the FindDataWidget now generate a AppendSelections proxy. Due to this change, the render view can now combine all selections types including frustum-based selections. Show frustum button has been removed, because 1) it's not used, 2) and visualizing more than one frustum would be highly confusing for the user.
4. vtkSelectionConverter has been deleted because it's no longer used.

VTK Updates:

1. vtkPIOReader: fix hang during parallel execution of reader
2. ci: exclude TestCookieCutter4 on Windows with STDThread
3. vtkSphericalPointIterator: include <memory> for std::unique_ptr
4. Add 1D convolution function
5. vtkMergeTimeFilter correctly supports non-temporal input
6. Selection Improvements
7. ci: exclude TestCookieCutter4 on all stdthread builds
8. TestDataArraySerialization: renaming and fixing compile issue

This MR will be merged once vtk/vtk!8871 (merged) is also merged.