Feature/collider and layer cleanup

[fernando-cortez]

Jira task here.

Changes:

• Colliders on floor dungeon pieces are enabled on the prefab, but now get disabled on Awake(). This is the best tradeoff I found for reducing total colliders inside of BossRoom scene, but still allowing re-baking of the NavMesh. This also provides the most accurate NavMesh if it uses the actual floor tile colliders.
• To provide a surface to enable player navigation, a plane with MeshCollider now covers all of Dungeon and is on "Ground" layer. This plane is disabled by default inside of Dungeon prefab but is enabled on Awake().
• AoE action has been slightly modified to check against a NavMesh surface instead of a ground collider, since now there is a plane that covers all of the level. This means that you can still only use AoE actions inside of the walkable level area. Will be a net benefit since we remove raycast calls from an Update() method.
• Removed colliders on "top" wall prefabs as they did not contribute to gameplay or navigation.
• Removed NavMeshObstacle components from prefabs as these prefabs only needed to be added to "Ground" layer to affect the generated NavMesh.
• Removed references to unused "HeavyObject" layer inside of ServerFloorSwitch, and subsequently removed from layers altogether.
• Removed old generated NavMeshes and renamed the newest one.
• Physics layer matrix cleaned up with now less possible layer interactions.
• Made a fix to my previous PR's scrolling UVs modification. This can be simply be done inside one single behaviour with a reference to the material. ScrollingUVs component is removed from lava prefabs. The laval material will also not get marked up by git as modified.

Some before and after screenshots of Physics profiler section: