Misc SurfaceData Optimizations (#7299)

* Misc SurfaceData Optimizations.
This includes a few different optimizations found while trying to make the bulk query APIs faster:
* Switches mutexes over to shared_lock to optimize for the multi-reader-single-writer pattern
* Surface provider point creation now uses a pre-created set of masks to initialize with, and uses std::move() to move the created point into the output list instead of copying it.
* Splits CombineSortAndFilterNeightboringPoints so that the FilterPoints() can occur separately and efficiently with erase/remove_if, and avoids making a copy of the output points.
* Optimized SurfaceDataShapeComponent::ModifySurfacePoints
* Fixed potential bug where the sort wasn't stable since it only compared the Z value, and could have produced unexpected results for differing points with the exact same Z value.
* Fixed up a couple small bugs and missing checks in the unit tests

Signed-off-by: Mike Balfour <82224783+mbalfour-amzn@users.noreply.github.com>

* Fixed syntax on unit tests.

Signed-off-by: Mike Balfour <82224783+mbalfour-amzn@users.noreply.github.com>

Gems/Terrain/Code/Source/Components/TerrainSurfaceDataSystemComponent.cpp

@@ -177,7 +177,7 @@ namespace Terrain
         const AZ::Crc32 terrainTag = isHole ? Constants::s_terrainHoleTagCrc : Constants::s_terrainTagCrc;
         point.m_masks[terrainTag] = 1.0f;
 
-        surfacePointList.push_back(point);
+        surfacePointList.push_back(AZStd::move(point));
     }
 
     AZ::Aabb TerrainSurfaceDataSystemComponent::GetSurfaceAabb() const