Prepare for adaptive cache testing with a known-nulls cache. This existed probably over a year ago as well but was removed. Basically:

It is just a cache of blocks that are known to not have any protections on them. If all protections are not in the cache then an otherwise cache miss would force a DB lookup. This prevents that DB lookup after the first time it's done (and nothing is found)
Fix a somewhat long standing bug where you might see "grass" or something protected when removing one side of a double chest and placing a block down where it was before. Other removeCache calls are to assist with the known null cache
New adaptive cache increasing which can be requested by high-intensity code areas. /lwc admin report now lists the default and adaptive cache size, e.g. ( 1252/1260 [100+1160] ) = 100 default cache size (core.yml) + 1160 adaptively increased because a high-intensity code area needed it.

PS this is of course in very much testing. I expect this to work well in the long run but of course some minor issues may come up here and there.