This improves the defragment operation for chonks by letting them remove
chunks at the top that match above, and bottom that match below. This
reduces the chunks / chonk from around 5.9 to around 3.4 at origin. From
my investigations, adding something for water would probably get us a
full 50% reduction, if we could collapse intermediate chunks; block
types other than rock / air / water never appear to have full chunks of
the same block, so any additional optimization will require changes to
the subchunk compression format or changes to the actual chunks we
generate.
After generating a chonk, we now find the highest frequency block (in
terms of the number of groups that uniformly consist of that block) and
replace the chunk's default with that one. We also resort the data in
the process to be in the same order as the original array index. This
improves our memory savings from 3x to almost 7x, and brings us within a
factor of 3 or so of what I hope a true average will be.
The defragmentation is not totally optimal and can probably be improved
from a performance perspective, but given how much of a hard bottleneck
RAM is this seems worthwhile. Also, this doesn't suffer from the issues
the previous solution did.
3x - 5x depending on terrain. We can do a lot better but this is a good
start.
Also, added chunk group count to metrics. This correlates with memory
usage specifically by chunk voxel data in a much more direct way than
chonk or chunk count do, so this should provide extra useful information
(especially for our average overhead per chonk / chunk).
In the process, also try to address a few edge cases related to block
detection, such as adding back previously solid sprites and removing
filters that may be vestiges of earlier logic.
