[feature][processing] Random points in polygons C++ algorithm

Offers the same functionality as the Random points inside polygons
algorithm, and in addition it includes (possible to opt-out) the attributes
from the containing polygon and the ability to specify a seed for the random
number generator.

Could replace the Python algorithm Random points inside polygons, but
this C++ implementation only supports "Points count" ("number of points
for each feature") directly, while "Points density" is supported by allowing the
point count to be data defined (using the polygon area to calculate the
number of points).

images/images.qrc

@@ -115,6 +115,7 @@
         <file>themes/default/algorithms/mAlgorithmPolygonToLine.svg</file>
         <file>themes/default/algorithms/mAlgorithmRandomExponentialRaster.svg</file>
         <file>themes/default/algorithms/mAlgorithmRandomGammaRaster.svg</file>
+        <file>themes/default/algorithms/mAlgorithmRandomPointsInPolygons.svg</file>
         <file>themes/default/algorithms/mAlgorithmRandomPointsOnLines.svg</file>
         <file>themes/default/algorithms/mAlgorithmRandomPointsWithinPolygon.svg</file>
         <file>themes/default/algorithms/mAlgorithmRandomPointsWithinExtent.svg</file>

python/plugins/processing/gui/menus.py

@@ -58,7 +58,9 @@
                            'qgis:randomselectionwithinsubsets': researchToolsMenu,
                            'native:randompointsinextent': researchToolsMenu,
                            'qgis:randompointsinlayerbounds': researchToolsMenu,
+                           'native:randompointsinpolygons': researchToolsMenu,
                            'qgis:randompointsinsidepolygons': researchToolsMenu,
+                           'qgis:randompointsonlines': researchToolsMenu,
                            'qgis:regularpoints': researchToolsMenu,
                            'native:selectbylocation': researchToolsMenu,
                            'native:polygonfromlayerextent': researchToolsMenu})