#13967 RigMainGrid: Invalidate face-normal direction cache on setFlipAxis

isFaceNormalsOutwards lazily computes whether cell face normals point outward
and caches the answer in m_isFaceNormalsOutwardsComputed. setFlipAxis was
mirroring the node coordinates without resetting that cache, so any consumer
that had triggered the lazy computation before the user toggled Flip X/Y kept
the pre-flip answer. The well-path/cell intersection in
RigEclipseWellLogExtractor::calculateIntersection then inverted the
entering/leaving flag the wrong way, causing the proper-pair filter in
populateReturnArrays to discard every intermediate cell along a perforation
interval - only the start and end cells survived through the
well-starts/ends-inside-a-cell fallback.

Reset m_isFaceNormalsOutwardsComputed when the flip state actually changes.

Add unit tests covering all four combinations of Flip X / Flip Y for both the
data-level node mirroring and the well-path/cell intersection (freshly-built
grid and interactive-toggle scenarios).

ApplicationLibCode/ReservoirDataModel/RigMainGrid.cpp

@@ -349,6 +349,9 @@ void RigMainGrid::setFlipAxis( bool flipXAxis, bool flipYAxis )
 
         m_flipXAxis = flipXAxis;
         m_flipYAxis = flipYAxis;
+
+        // Cell face normals flip direction with the geometry, so a cached value computed before the flip is stale.
+        m_isFaceNormalsOutwardsComputed = false;
     }
 }