Fix legend feature count / WMS content based legend when using size scale / rotation field

symbolForFeature() / symbolsForFeature() may return temporary symbols
in some renderers when using size scale or rotation field, which makes
it impossible to identify which legend item is really used. The new "original"
variants of the features return non-modified symbols that can be accessed
by e.g. legendSymbolItemsV2()
Use exact intersection for hit test in WMS content based legend

Otherwise it may include legend items of features which only have
bounding box intersecting the map view, but not their real geometry
Merge branch 'wms-content-based-legend' into wms_legend