perf: improve performance of mesh generator for chunks

[pollend]

some minor performance tweaks to mesh generation. so one bottleneck I found is we evaluate the sides of all the blocks for every block within the chunks so each block will check all its ordinals even if it is lets say its air which has no geometry. API is coupled to the block so mesh information is defined by the block itself. would like this to be more data oriented but that is something to consider later.

I also swapped out the maps for switch cases for BlockParts which should also help to some extent.

hard to test all the permutations so just verifying that chunks render correctly for a couple different types of blocks will be sufficient.

[skaldarnar]

@pollend did you check the rest of Omega for any broken code with this? At least in a MetalReneages workspace this does not compile:

> Task :modules:MetalRenegades:compileJava FAILED
/home/skaldarnar/Code/movingblocks/ts-mr/modules/MetalRenegades/src/main/java/org/terasology/metalrenegades/world/dynamic/roads/RailRasterizer.java:65: error: cannot find symbol
        for (Side side : Side.getAllSides()) {
                             ^
  symbol:   method getAllSides()
  location: class Side