Implement Lager-based brush editor backend

This merge request is in work-in-progress state, its main goal right now is to gather early feedback only, it is not intended to work too correctly

WARNING: the patch changed C++ standard to C++17, so it will require full rebuild!

Documentation about the Lager port: https://docs.krita.org/en/untranslatable_pages/brush_editor_gui_with_lager.html

Tasks list

Done:

1. KisTangentNormalPaintOp (@freyalupen)
2. KisCurvePaintOp (@tymond)
3. KisExperimentPaintOp (@tymond)
4. KisRoundMarkerOp (@freyalupen)
5. KisSketchPaintOp (@freyalupen)
6. KisHairyPaintOp (@freyalupen)
7. KisMyPaintPaintOp (@dkazakov)
8. KisDeformPaintOp (@freyalupen)
9. KisParticlePaintOp (@freyalupen)
10. KisDuplicateOp (@szaman)
11. KisHatchingPaintOp (@freyalupen)
12. KisSprayPaintOp (@tymond and @dkazakov)
13. KisGridPaintOp (@tymond)